JPH07161680A - Etching method and device - Google Patents

Abstract

PURPOSE:To judge that etching solution is deteriorated or not in quality by a method wherein two etching masks of sparse pattern and dense pattern are formed on an etched film, the film is etched, and the ratio between etching times required for removal of the two parts of the film where the two etching masks of sparse and dense pattern are provided is obtained. CONSTITUTION:A sparsely patterned resist film and a densely patterned resist film are formed on a Cr film deposited on a monitoring glass board 9, the glass board 9 is set in a monitoring tank 6, and an etched film is subjected to an etching process. At this point, etching times required for complete removal of the two parts of the etched film where the two etching masks of sparse and dense patterns are provided are optically monitored by an observing means 10 through which the intensity of reflected light from the Cr film is observed, and the ratio between the two monitored etching times is calculated, whereby it is judged that etching solution is deteriorated or not. By this setup, the deterioration of etching solution can be accurately detected, so that an etching operation can be improved in accuracy.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an etching method,
In particular, the present invention relates to an etching method capable of monitoring deterioration of an etching solution.

Since the etching solution deteriorates when the same etching solution is continuously used, in order to continue normal etching, it is necessary to monitor the degree of deterioration of the etching solution and replace it with a new etching solution.

[0003]

2. Description of the Related Art As a conventional method for monitoring the deterioration of an etching solution, the specific resistance of the etching solution, the analysis of the composition, the number of wafers subjected to etching treatment, or the just etching time (etching end point) at which the same pattern is completely removed by etching Time) and the like.

[0004]

In the prior art, since the etching itself is not directly monitored, the accuracy of determining the replacement time of the etching solution is poor. If the replacement time is incorrect and a deteriorated etching solution is used, proper etching cannot be performed, and conversely, the undegraded etching solution may be discarded.

An object of the present invention is to provide a monitor capable of accurately detecting deterioration of an etching solution.

[0006]

[Means for Solving the Problems] 1)
Etching is performed on the etching target film by forming an etching mask of a sparse pattern and a dense pattern on the etching target film, and then etching is performed by obtaining a ratio of just etching times at which the etching target film of each pattern is completely removed by etching. Etching method for judging deterioration of liquid, or 2) Etching tank for etching processed material
1, a monitor tank 6 for sampling an etching solution from the etching tank, a monitor substrate 9 which is immersed in the monitor tank and on which a coating of a sparse pattern and a dense pattern is formed, and a sparse pattern and a dense pattern of the monitor substrate And an observing means 10 for determining the just etching time of the film.

[0007]

In the present invention, when the deterioration of the etching solution progresses,
As a result of experiments, it was found that the difference in the just etching time between the sparse pattern and the dense pattern is large, and this phenomenon is used.

Now, an explanation will be given by taking as an example the etching of a chromium (Cr) film used as a light shielding film of a mask in a photolithography process in the manufacture of a semiconductor device. Usually, Cr
Wet etching of ceric ammonium nitrate
An aqueous solution of [Ce (NO ₃ ) ₄・ 2NH ₄ (NO ₃ )] is used and is represented by the following formula.

3Ce ⁴⁺ ＋ 3e ＝ 3Ce ³⁺ Cr → Cr ³⁺ ＋ 3e ────────── 3Ce ⁴⁺ ＋ Cr → 3Ce ³⁺ ＋ Cr ³⁺ Therefore, the more Ce ⁴⁺ is, the stronger the etching strength is. Become. When Ce ⁴⁺ decreases with continued etching with the same etching solution, the etching strength decreases. The same phenomenon occurs when the concentration of ceric ammonium nitrate in the aqueous solution is changed.

Therefore, how the just etching of the sparse pattern and the dense pattern was changed by changing the concentration of ceric ammonium nitrate was observed by an optical monitor.

2A and 2B are explanatory views of the principle of the present invention. Figure 2 (A) shows the concentration of ceric ammonium nitrate.
Shows the film thickness of chromium with respect to the etching time for 40 wt% and Fig. 2 (B) for 17 wt%, and the time when the film thickness becomes zero is the just etching time.

The parameters in the figure indicate a sparse pattern and a dense pattern, which are the pattern to be etched, and the dotted line is 10 mm □.
The sparse pattern and solid line are 2 μm line and space (L & S).

The concentration of ceric ammonium nitrate is 40
The ratio of the just etching time of the coating of the sparse pattern and the dense pattern is 28.4 s / 26.6 s = 1.06 when the concentration of cerium ammonium dinitrate is 17 wt%. The etching time ratio is 36.9 s / 24.6 s = 1.50.

Further, although not shown, when the same concentration is 9 wt%, the ratio of the just etching time of the coating of the sparse pattern and the dense pattern is 3.37. As a result, it can be seen that the just etching time ratio of the coating of the sparse and dense pattern increases as the etching solution deteriorates.

Therefore, it is possible to judge the deterioration of the etching solution by preparing the sparse / dense pattern and monitoring the just etching time thereof. That is, the deterioration of the etching solution is represented by the ratio of the just etching time of the sparse pattern and the dense pattern. At this time, in order to prevent deterioration of the etching solution due to monitoring of the etching solution deterioration, it is desirable to provide a tank for sampling the etching solution separately from the processing tank.

[0016]

[Embodiment] Here, etching for forming a Cr pattern having a thickness of 1000Å on a glass substrate will be described.

As a mask for etching Cr, an ordinary resist pattern formed by exposing a resist is used. FIG. 1 is a configuration diagram of an etching apparatus used in an embodiment of the present invention.

In the figure, the etching solution is constantly circulated by a pump 3 through a pipe provided with a filter 2. The etching solution used to monitor the deterioration is sampled by opening the valve 7 through the piping introduced from the etching tank 1 to the monitor tank 6. Here, the etching solution used for one monitor is 30 cc.

As the monitor substrate 9 on which the sparse pattern and the dense pattern are formed, the Cr film deposited on the glass substrate is used similarly to the substrate to be etched, and the resist film is formed on the sparse pattern of 10 mm □ (10 mm □). Part without resist pattern, that is, part where Cr film is exposed) and 10 mm
A dense pattern of L & S of 2 μm is formed.

An ordinary optical monitor was used as the observation means 10 for determining the just etching time, and the intensity of the reflected light from the Cr film was observed. The reflected light from each of the sparse and dense patterns is received by a light receiving element such as a photodiode, narrowed into a band through a filter, and the intensity is A / D converted and input to a computer, and the computer calculates the ratio of just etching times of both patterns. To be done.

When the monitor tank 6 is filled with the sampled etching solution, the monitor substrate 7 on which the sparse and dense pattern is formed is immersed in the monitor tank. Then, the ratio of the just etching time of the dense pattern is calculated.

When this ratio exceeds a set value, it is determined that it is difficult to form a pattern having a desired dimensional accuracy due to deterioration of the etching solution, and the valve 4 is opened to drain the etching solution from the drain 5. After draining the liquid, the pump 8 works and a new etching liquid is supplied from the outside into the etching tank 1. Then, the etching process of the substrate to be processed is restarted.

When the ratio of the just etching time of the sparse and dense pattern is equal to or less than the set value, the etching is used as it is and the etching process is continued. Here, the new etching solution has a concentration of ceric ammonium nitrate of 40 wt.
% Aqueous solution was used, and the set value of the ratio of just etching time was 1.15.

As a matter of course, the monitor substrate is replaced for each monitor. In the examples, a chromium film was used as the object to be etched and ceric ammonium nitrate was used as the etching solution, but the present invention is not limited to these, and the concentration of the etching solution is also limited to that of the examples. Not done.

[0025]

According to the present invention, the deterioration of the etching solution can be detected with high accuracy, and the etching accuracy can be improved. As a result, it is possible to contribute to improvement in precision of fine processing in the manufacturing process of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an etching apparatus used in an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the principle of the present invention.

[Explanation of symbols]

 1 Etching tank 2 Filter 3 Pump 4 Valve 5 Drain 6 Monitor tank 7 Valve 8 Pump 9 Monitor substrate on which sparse and dense patterns are formed 10 Observing means to judge just etching time

Claims (2)

[Claims] 1. A just etching time period in which an etching mask having a sparse pattern and a dense pattern is formed on a film to be etched to etch the film to be etched, and the film to be etched having each pattern is completely removed by etching. An etching method characterized in that deterioration of an etching solution is determined by obtaining a ratio. 2. An etching tank (1) for etching an object to be processed, a monitor tank (6) for sampling an etching solution from the etching tank, and a sparse pattern and a dense pattern film immersed in the monitor tank. Monitor board
(9) and an observation means (10) for determining the just etching time of the coating of the sparse pattern and the dense pattern of the monitor substrate
An etching apparatus comprising: