JPH04100227A - Etching process of thin film - Google Patents

Abstract

PURPOSE:To avoid any residual etching process by a method wherein the over- etching time is set up conforming to the fluctuation time of etching light intensity wave form near the etching terminal point using the value proportional to this fluctuation time. CONSTITUTION:The overetching time is set up conforming to the fluctuation time of etching light wave form near the etching terminal using the value proportional to this fluctuation time. When an aluminum thin film 6500Angstrom is etched away using a parallel-plate type plasma etching device, the linear differential of observed wave form is simultaneously counted to decide the wave form and then the quardratic differential value is further counted to decide the wave form. At this time, -0.5V is set up as the threshold value so as to assume the points not exceeding the threshold value as the wave form fluctuation time. Next, the etching terminal point is set up while the time detecting this point shall be stored in a storage. Finally, the time difference is counted to be set up as the wave form fluctuation time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to automatic control of the end of etching in the process of etching thin films, particularly dry etching.

[Summary of the invention]

In the present invention, the additional etching amount during etching is determined by measuring the change time of the etching emission intensity waveform based on the waveform data of the plasma emission intensity during etching, and calculating the additional etching amount after the etching completion judgment in the form of a constant times the change time. This is to establish the following.

[Conventional technology]

Patterning of thin films has conventionally been commonly performed using resist. This method involves coating a thin film with a photosensitive material, baking a pattern onto it, and developing it. First, a resist pattern is formed. Next, when the entire surface is etched, the thin film in areas without resist is scraped off, while the resist pattern is etched. Buttering of the thin film is performed in such a way that a certain portion of the thin film remains. At this time, the resist pattern is not necessarily transferred exactly as it is to the thin film, but is slightly deformed. A dry etching method was developed to reduce this degree of deformation. In this dry etching method, a voltage is applied between electrodes to generate plasma, and a thin film is formed through a gas phase reaction by active species generated in the plasma. At this time, in order to determine the completion of etching, it is common to monitor changes in the emission intensity of the plasma and obtain the etching waveform. This light emission is observed when the thin film is being etched, but once the thin film is completely etched, this light emission is no longer observed. Therefore, by observing the temporal change in the light emission intensity, the end point of etching can be determined. However, if etching ends at the etching end point detected in this way, etching remains will be left behind.This may be due to variations in the thickness of the thin film, variations in the etching speed, or local changes in the film thickness due to irregularities in the underlying layer. For this reason, a certain amount of etching is added after the completion of etching is determined.This is called over-etching.

Conventionally, the amount of over-etching has been set as a fixed amount of time or as a percentage of the time required to complete etching. That is, to explain it along the lines of FIG. 2, the time 9 between the etching start point 6 and the etching point 8 is set as the etching time, and some percentage of this time is set as the overetching time 10, and the etching end point 7 is set as the overetching time 10. It is added after.

[Problem to be solved by the invention]

However, in the conventional method, etching residues may occur due to increased variations due to changes in the conditions of the etching equipment. This is explained as follows. As mentioned in the conventional technique, the overetching amount is set to absorb etching residue due to variations in film thickness and etching speed, so naturally, if the variations become large, the overetching amount must be increased by that amount. However, even if the variation fluctuates, the etching time 9
does not change much, so the overetching time 10, which is determined in proportion to 9, does not increase much either. For this reason, there was a problem in that an etching residue was generated.

[Means to solve the problem]

In order to solve the above problem, the present invention sets the overetching time based on the change time of the etching light emission waveform near the etching opening point using a value proportional to the change time of the etching waveform.

[Effect]

The operation of the present invention will be explained with reference to Fig. 1.0 As pointed out in the section ``Problems to be Solved by the Invention'', the etching residue is removed by normal over-etching when variations in film thickness and etching speed become large. This occurs when the amount is insufficient. Therefore, the variation in film thickness and etching speed can be detected and the amount of overetching can be changed accordingly.The overall etching variation can be evaluated by the waveform change time of the luminescence intensity during etching shown in FIG. The principle of generation of the edaturing waveform change time is as follows. If the film thickness and etching rate vary, there will be regions where etching ends earlier and regions where etching ends later. Then, the etched film disappears from the part where the etching was completed earlier, so the etched area gradually becomes smaller. Eventually, all the membranes disappear.

As can be seen from the above explanation, when the variation is large, the film disappears quickly, and at the same time, it becomes slower for the film to completely disappear. In other words, the time at which the luminescence intensity begins to drop, which is the vertical axis, becomes earlier, and the time shown in FIG. 1, which is the time until a certain constant luminescence intensity is reached, becomes longer. Therefore, if the overetching amount is set in proportion to that shown in Fig. 1, the overetching amount will increase as the dispersion increases.
Etching residue can be prevented from occurring.

〔Example〕

FIG. 3 shows a diagram of an etching control method for an aluminum thin film.

Specific Example 1 It is assumed that 6,500 aluminum thin films are to be etched using a parallel plate type plasma dry etching device.The program of a normal end point detection device is changed as follows. From the observed waveform shown in Figure 3 (al), the waveform shown in Figure 3 (b) is obtained by simultaneously calculating its negative derivative.Furthermore, the second derivative value is determined and shown in Figure 3 tc+. Obtain the waveform (from this in Figure 3), set -O, SV as the dark value, and set the point below this dark value in Figure 3 (bil
The zero-order enching end point with a waveform change time between 1 and 12 is set at a point 13 crossing the horizontal axis in FIG. 3 fcl. When this point is detected, this time is memorized. After that, when point 12 (in Fig. 3) is detected, point 1
The time difference between point 2 and point 11 is calculated and set as the waveform change time. Adding 1.3 times the waveform change time obtained in this way to the time corresponding to point 13 in Fig. 3(C),
The etching stop time was determined, and etching was continued until this time.

Concrete Example 2 In Concrete Example 2, point 12 in FIG. 3 1b) is set as the end point of etching without using the second-order differential in FIG. 3 [0].

Then, as in Example 1, the difference between points 11 and 12 in Figure 3) is defined as the waveform change time, and the time obtained by adding this waveform change time to the time at point 12 in Figure 3Cb) is defined as the etching stop time. Etching was carried out up to this time.

C. Effects of the Invention] As explained above, this invention detects variations in film thickness and etching speed by measuring the waveform change time of the luminescence intensity during thin film etching, and calculates the amount of overetching in proportion to this change time. This setting has the effect of preventing etching residue from occurring.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an overetching amount setting method according to the present invention, FIG. 2 is an explanatory diagram of a conventional overetching amount setting method, and FIG. 3 is a diagram showing an etching control method in an embodiment. 1, 6 ・ 2, 7 ・ 3, 8 ・ 4 ・ ・ ・ 5, 10 ・ 9 ・ ・ ・ 11 ・ ・ Etching start point Start point of waveform change area End point of waveform change area Waveform change time Over etching time Etching Starting point 12 of the waveform change area used in the time examples...End point 13 of the waveform change area used in the examples...Etching end point used in Example 1 Applicant: Seiko Electronics Co., Ltd. Yoshiyuki Hayashi, Patent Attorney, Agent Co., Ltd. Diagram 1 of the method for determining Ohartso + amount 3q according to the invention of Hikigi? Legs 3! 'no(-Heart Utton Hole L7ffi17>
Prayers for June, Figure 2, Koyu Qiang (v)

Claims (1)

[Claims] In a thin film etching method that includes a means for monitoring a light emission state during an etching reaction and a means for controlling etching based on data on temporal changes in light emission intensity obtained by the monitoring means, the etching light emission intensity waveform near the etching end point is A thin film etching method characterized in that, based on a change time, a value proportional to the change time is set as an additional etching amount after etching completion determination.