JPS627880A - Plasma etching device - Google Patents

Abstract

PURPOSE:To absorb the variance of the quality and thickness of the film of a material to be treated and to carry out etching treatment stably and accurately by providing an arithmetic mechanism for automatically calculating the overetching time from the time when the light intensity of plasma reaches a prescribed value. CONSTITUTION:The end point of a reaction is detected by an end point detector 10 having a mechanism for monitoring the light intensity of plasma through an optical fiber 8 and the end point is detected. Overetching is then carried out. The overetching time is automatically obtained by an arithmetic mechanism housed in the detector 10 and used for calculating the overetching time by muliplying the etching time by a prescribed factor. after overetching, the whole process is stopped and t etching is finished. By such a constitution, the overetching time is prolonged when the film is thick and the overetching time is reduced when the film is thin. Desired etching can be carried out in this way.

Description

[Detailed description of the invention] The present invention relates to a plasma etching apparatus.

In the manufacture of semiconductor devices, plasma etching is used as a technique to partially remove films such as polysilicon and nitride (Si3H4) formed on the surface of semiconductor thin plates (margins...). .

As one of the etching completion operations (controls) in this plasma etching method, a method of monitoring the intensity of plasma light is adopted. That is, as shown in FIG. 1, in order to perform plasma etching, the wafer 2 is placed on the stage l, then covered with a quartz belljar 3, and the air in the chamber 5 is evacuated from the exhaust pipe to achieve the desired vacuum. Increase the degree. Thereafter, a voltage is applied to the ti6 and, for example, Freon gas (CF4) is ejected from the gas injection tube 7 to excite plasma in the chamber 5, thereby etching, for example, the polysilicon film not covered by the photoresist film on the wafer 2 surface. . In this case, an optical fiber 8 having an optical filter attached to its tip is disposed outside the belljar 3, and a detector 9 monitors changes in the intensity of plasma light during etching using the optical fiber 8. This detector 9 has a highly sensitive phototransistor, which photoelectrically converts the amount of detected light to draw a waveform as a voltage change. During this monitoring, as shown in Fig. 2, the end point (Pg) when the plasma light intensity (I) reaches a predetermined intensity is detected and the etching is completed.
It is said that

On the other hand, in order to improve variations in film thickness of polysilicon, etc., deviations in processing equipment conditions, and improvement in dimensional accuracy, a so-called overetching process is employed in which etching is continued for a predetermined period of time even after endpoint detection.

Conventionally, this overetching time is digitally determined to be, for example, 10 seconds. However, if the overetching time is uniformly determined in this way, variations will occur depending on whether the film is thick or thin. On the other hand, if the film quality differs, the etch rate will also change. Therefore, it is difficult to uniformly determine the overetching time.

Therefore, an object of the present invention is to absorb variations in film thickness and film quality and perform stable plasma etching.

The present invention will be explained below with reference to Examples.

FIG. 3 shows a plasma etching apparatus according to one embodiment of the present invention. The figure shows a stay 1 on which sea urchins 2, which are objects to be treated, are placed. Also, stay) 1
A bell jar 3 made of quartz is disposed above the stay 1 so as to move toward and away from the stay 1. Additionally, an exhaust pipe housing is attached to Belljar 3. Further, the stage 1 is provided with an electrode 6 and a gas injection pipe 7. on the other hand,
An optical fiber 8 having an optical filter attached to its tip is disposed outside the belljar 3. The other end of this optical fiber 8 is connected to a reaction end point detector (end point detector) 10. This endpoint detector 10 has a monitoring mechanism that monitors the margin below the plasma light intensity, and the endpoint (Pm)
An arithmetic logic unit (Arithmat icLogic Unit) that detects the etching time of the object to be etched and calculates the overetching time by multiplying the etching time of the object to be etched by a predetermined rate.
)have. The endpoint detector IO is also provided with an overetching time display section 11.

The endpoint detector 10 also serves as a control mechanism for controlling a plasma etching mechanism consisting of a stage, a bell jar, and the like.

According to such a plasma etching apparatus, after the wafer 2 in the chamber 5 is brought to a desired degree of vacuum, a voltage is applied and a predetermined gas is flowed through the gas injection tube 7 to perform plasma etching. After detecting the end point of the reaction by monitoring the intensity of the plasma light, the process is transferred after over-etching, and after over-etching, the entire process is stopped to complete the plasma etching. Note that the etching time is automatically determined by a calculation mechanism.

For example, the etching time for one punch is determined by determining the etching time of the object to be treated, and then adding 20 points to that value (in seconds).

According to this type of plasma etching, when the film thickness is thick (when the etching rate is low), the overetching time is increased, and when the film thickness is thin (when the etching rate is high), the overetching time is shortened. , the desired etching can be performed.

Note that the present invention is not limited to the above embodiments.

As described above, according to the plasma etching of the present invention,
Accurate etching can be performed by absorbing variations in film quality and film thickness of the object to be processed.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional plasma etching device, Figure 2
The figure is a graph showing the light intensity of plasma during plasma etching, and FIG. 3 is a schematic diagram showing a plasma etching apparatus according to an embodiment of the present invention. l...Sf--;, 2...Wafer, 3...4 Lusia, 4...Exhaust pipe, 5...Chamber, 6...Electrode, ? ...Gas injection tube, ...Optical fiber, 9
...Detector, 10...Reaction end point detector, 11...
Oh, + etching time display section. Figure 1 Figure 2 rfJ (sec)

Claims (1)

[Claims] 1. Time taken for the plasma light intensity to reach a predetermined intensity in a plasma etching apparatus that has a plasma etching mechanism, a monitor mechanism that monitors the plasma light intensity, and a control mechanism that controls the plasma etching mechanism based on data from the monitor. A plasma etching apparatus characterized by having a calculation mechanism that automatically calculates an overetching time from .