JPS6199332A - Plasma etching method - Google Patents

Abstract

PURPOSE:To enable patterning at a constant speed in high accuracy removing a deposit film by carrying out plasma treatment with oxygen gas in plasma etching. CONSTITUTION:A deposit film is formed by plasma etching to a definite film thickness with a carbon fluoride series gas including hydrogen. Then, the deposit film is removed by plasma treatment with oxygen gas. If the plasma etching and the plasma treatment are carried out alternately, the etching can be advanced at a constant speed. Further, since a resist film can be incinerated by oxygen gas plasma and removed, if the changeover of a treatment time is appropriately adjusted, a resist film pattern is also removed at the time of patterning finish and the simplifying of a photo process can also be possible omitting the process of removing the resist film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma etching method, and for example, to a plasma etching method for an insulating film in a semiconductor device manufacturing process.

In the wafer process for manufacturing semiconductor devices, dry etching is used to miniaturize and increase the integration of semiconductor devices, but recently, among these dry etching methods, plasma etching methods have been particularly important. It has become.

The plasma etching method is a method in which a reactive gas is excited by high-frequency discharge, turns into plasma, is brought into contact with the film to be processed, and the film to be processed is gasified and removed through a chemical reaction with radicals in the plasma. In addition, it has the advantage of being able to be etched with high precision.

However, depending on the type of reaction gas, reaction products may remain, and new countermeasures are required for plasma etching in such cases.

[Prior Art] Fig. 2 is a schematic sectional view of a plasma etching apparatus, in which 1 is a reaction chamber, 2 is a reaction gas inflow, 3 is a vacuum exhaust port, 4, 5
is a counter electrode, 6 is an insulator, 7 is a sample to be processed (semiconductor substrate), RF is a high frequency oscillator (frequency: 13.56MH
z) indicates tail.

A semiconductor substrate as shown in the cross-sectional view of FIG. 3 is loaded into such a plasma etching apparatus, and plasma etching is performed using a reaction gas as described below.

In FIG. 3(a), 11 is an n-type semiconductor substrate (wafer), 12 is a p-type region, and 13 is a silicon dioxide film (S'
i02 III), 14 indicates a resist film pattern, and using this resist film pattern 14 as a mask, 5iO
2111I! 13, the semiconductor substrate is loaded into the etching apparatus shown in FIG. , for example trifluoromethane (CHF a
) Gas is introduced from the reaction gas inlet 2.

Thus, the degree of vacuum in the reaction chamber 1 is set to 0.1 to I Tor.
r, high-frequency power is applied between both electrodes 4 and 5 to turn the reactive gas into plasma and form the resist film pattern 14.
The 5i02 film 13 exposed from above is etched.

[Problems to be solved by the invention] Then, as shown in the cross-sectional view of the process shown in FIG. 3(b),
The 5i02 film 13 begins to be etched, but on the other hand, a deposit film 15 is generated by the plasma gas that has come into contact with the resist film pattern 14, and for example, a deposit film 15 with a film thickness of 5,000 mm is formed.
When opening a window in the i02 film 13, if the edge is etched to a thickness of several hundred layers, the deposited film 15 will cover the surface, slowing down the etching speed, and eventually stopping the etching process.

When etching becomes unstable in this way, patterning accuracy also deteriorates, and etching cannot be performed unless this deposited film is removed.

The present invention proposes a plasma etching method for removing such a deposit film and patterning it at a constant speed and with high precision.

[Means for solving the problem] The problem is that in the process of plasma etching a sample to be processed with a resist film mask provided with a fluorocarbon gas containing hydrogen, during the plasma etching process, the etching process is performed using oxygen gas. The problem is solved by a plasma etching method that performs plasma treatment.

For example, there is a plasma etching method in which plasma etching using a carbon fluoride gas containing hydrogen and plasma processing using oxygen gas are performed alternately, so that the removal of the resist film mask and the opening of the sample to be processed are completed at the same time. Let's do it.

[Function] That is, when a certain film thickness is plasma etched using a fluorocarbon gas containing hydrogen, a deposit film is generated. Therefore, next, plasma treatment using oxygen gas is performed to remove the deposited film.

Thus, by alternately performing plasma etching and plasma treatment, etching can proceed at a constant rate. Furthermore, since the resist film is ashed and removed by oxygen gas plasma, if the processing time is properly switched, the resist film pattern will be removed at the same time as patterning is completed, and the process of removing the resist film can be omitted. It also becomes possible to simplify the photoprocessing process.

[Example] Examples will be described in detail below with reference to three drawings.

FIGS. 1(a) to (dl) show step-by-step sectional views according to the present invention, and FIG. 1(a) is similar to FIG. 3<21).
A p-type semiconductor substrate 11 is provided with a p-type head region 12, and in order to open the St O211i13 coated on the surface of the p-type head region 12,
FIG. 3 is a diagram showing a process in progress in which a resist film pattern 14 is formed.

Such a semiconductor substrate is loaded into the etching apparatus shown in FIG. 2, placed on the electrode 5, and trifluoromethane gas is introduced from the reaction gas inlet 2. Then, the first
As shown in Figure 2), when the exposed 5i02 film 13 is etched and removed by etching to a thickness of about 500 to 1000, a deposit film 15 is generated on the surface and covers the surface. .

Next, the trifluoromethane gas flowing into the etching apparatus is stopped, and then the oxygen gas is introduced from the reaction gas inlet 2. Then, as shown in FIG. 1(C), the deposited film is removed by oxygen gas plasma. At this time, the surface of the resist film pattern 14 is also partially ashed and removed.

In this way, the etching progresses by alternately switching the reaction gas flowing into the etching device between trifluoromethane gas and oxygen gas. Then, as shown in FIG. 1(d), the S:O2 film 13 will be opened and a small amount of the resist film pattern 14 will remain on the surface. The pattern 14 is incinerated with oxygen gas and completely removed.

By processing in this way, plasma etching can proceed at a constant speed, and the resist film pattern is also removed during the window opening process, making the subsequent resist film removal process unnecessary and simplifying the photo process. be done.

Although the above is an example in which trifluoromethane (cut) gas is used as the etching reaction gas, the present invention is generally applicable to etching using other hydrogen-containing fluorocarbon gases such as difluoromethane (CHF2'I gas). can do.

[Effects of the Invention] As is clear from the above description, according to the present invention, plasma etching can be easily performed, patterning accuracy can be improved, and the process can be simplified.

[Brief explanation of drawings]

Figures 1(a) to ((old) are cross-sectional views of the plasma etching method according to the present invention in the order of steps; Figure 2 is a schematic cross-sectional view of a plasma etching apparatus; Figures 3(a) and (b) are conventional 1 is a step-by-step sectional view of an etching method. In the figure, l is a reaction chamber of a plasma etching device, 2 is a reaction gas inlet, 3 is a vacuum exhaust port, 4.5 is an electrode, and RF
is a high frequency oscillator, 7 is a sample to be processed, 11 is a p-type semiconductor substrate, 12 is an n-type region, 13 is 5i
02 film, 14 is a resist film pattern 15 is a deposit film. σ D L to υ ℃νV

Claims (2)

[Claims] (1) In the process of plasma etching a sample to be processed with a resist film mask provided with a fluorocarbon gas containing hydrogen, plasma treatment with oxygen gas is performed during the plasma etching. Characteristic plasma etching method. (2) In the above process, plasma etching with hydrogen-containing carbon fluoride gas and plasma treatment with oxygen gas are performed alternately so that the removal of the resist film mask and the opening of the sample to be processed are completed at the same time. A plasma etching method according to claim 1, characterized in that: