JPS6327026A - Surface protecting method - Google Patents

Abstract

PURPOSE:To obtain the surface, on which a surface oxide film is not formed, even through exposure to the outside air by discharging a halocarbon gas onto a sample to shape a surface protective film, introducing an etching gas decomposed by Deep UV beams and removing the surface protective film through optical irradiation. CONSTITUTION:A resist 11 is ashed by oxygen plasma, CF4 is caused to flow through the same chamber, and plasma is generated for approximately thirty sec and the surface is treated. Consequently, a thin oxide film on a contamination layer 14 on an Si substrate 13 is removed, and a treatment protective layer 15, the surface of which is replaced with carbon and fluorine, is shaped. When Cl2 gas is caused to flow, evacuating the inside of the chamber, pressure is brought to 600 mTorr and Deep UV beams are projected, Cl2 gas is decomposed by Deep UV beams, and Cl radicals are generated. The generated Cl radicals etch the protective layer, 15 and the contamination layer 14. Accordingly, the surface on which the surface oxide film is not formed is acquired even through exposure into the outside air.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface protection method used in the manufacturing process of electronic devices and the like.

(Prior Art) Conventionally, for example, a natural oxide film is formed on the Si surface, and this serves as a protective film for the Si surface, but may also become a hindrance. In other words, it becomes an insulating layer, making regular crystal growth difficult, and when forming metal electrodes, contact resistance increases because of this insulating layer. Conventional techniques for solving this problem include wet etching using hydrofluoric acid, high temperature heat treatment at 800'' or more, and physical sputtering using ions to remove the natural oxide film.

(Problems to be Solved by the Invention) In the wet etching method, if there is an oxide film on other parts, it will also be etched, making it impossible to secure the desired process shape. On the other hand, high-temperature heat treatment cannot be used if impurity distribution in the semiconductor is redistributed due to high temperatures, or if there is a material on the same substrate that cannot withstand high temperatures. In physical sputtering using M, damage due to physical sputtering cannot be avoided.

Therefore, the purpose of the present invention is to eliminate the above-mentioned drawbacks and form a protective film surface that is less likely to generate a natural oxide film.
It is an object of the present invention to provide a method that can remove the protective film at low temperature and with low hot water loss, if necessary.

(Means for Solving the Problems) The surface protection method of the present invention involves discharging halocarbon gas or a gas containing halocarbon gas immediately after the dry etching or dry film forming process and before exposing the sample to the outside air to form a surface protection film. Deep
The method is characterized in that the surface protective film is removed by irradiation with UV light, and then the next step is performed in a vacuum.

(Function) The present invention solves the problems of the prior art by adopting the above-described configuration. For example, CF4.
CHF3. Gas plasma treatment using a carbon halide such as CF4 + H2 is performed. Thereafter, the C12, F'2. HCI, H
Photoetching is performed using F or the like. Then, the surface that has been plasma-treated with light and carbon halide gas is extremely difficult to oxidize and can be easily removed by photo-etching. A clean surface free from contamination appears, which is extremely advantageous for subsequent processing.

(Example) An example of the present invention is shown below.

FIG. 1 shows an example in which the method of the present invention is applied to a conventional process in which after 5i02 etching, resist and resist ashing are performed, and then CVD film formation is performed. First, in the figure (a), 5iO
212 was etched. Then, the etched surface forms a contamination layer on the Si substrate 13.
A contamination layer (hereinafter abbreviated as a contamination layer) 14 is formed. This layer contains sputtered materials during etching, particularly oxygen and carbon from the resist, or fluorine and carbon contained in the gas. This contamination layer 14 is SI
MS analysis revealed that there were approximately 150 people. Furthermore, the following (b
) The resist remains unremoved due to resist ashing in the oxygen plasma shown in the figure. Next, to remove this contaminant layer 14 by photo-etching, first remove the natural oxide film on the contaminant layer with an HF aqueous solution, or the contamination history due to oxygen that seems to have entered the mask by sputtering during etching. The thin oxide film must be removed.

Then, a wet process is involved, and the required 5
Up to i0212 will be etched. Therefore, in the present invention, the resist 11 is formed by oxygen plasma as shown in FIG. 1(a).
After ashing, CF4 is flowed into the same chamber and plasma is generated for about 30 seconds to perform surface treatment. Then, the Si substrate 13
The thin oxide film of the soil of the upper contaminant layer 14 is removed, and the treated protective layer 15 shown in FIG. The thickness of this processed protective layer 15 is about 20 to 30 layers, and under it there still remains a contaminant layer of about 100 layers from when the 5i0212 shown in Figure (a) was etched. Next, we move on to the growth process,
This film forming apparatus includes a device capable of irradiating deep UV light while flowing C12 or F2 gas in a vacuum, such as an excimer laser device or a Hg lamp. In Figure 1 (C), while evacuating, flow CI2 gas and reduce the pressure to 60
When irradiated with deep UV light at 0 mTorr, C
12 gas is decomposed by deep UV light and C1 radicals are generated. The generated C1 radicals can easily etch the treated protective layer 15 and the underlying contamination layer 14. FIG. 2 shows the relationship between C12 pressure and etching rate in this CI2 photoetching. Since there are about 150 people in the contaminant layer, in order to treat it in 1 to 2 minutes, it will take about 50 to 70 people/mi.
It is only necessary to select a C12 pressure that provides an etching rate of n. Figure 3 shows the concentration of carbon and fluorine during contamination layer etching with C12 photoetching time.
It was measured by analysis. It can be seen that the treated protective layer and contaminant layer were removed by etching for about 2 minutes. The carbon concentration will drop to about the same level as the carbon pollution caused by carbon dioxide gas in the air.

Next, regarding this principle, the Si surface is easily oxidized, but the protective layer treated by the plasma treatment of the present invention is extremely difficult to oxidize. An example showing this is shown below.

Table 1 Table 1 shows the etching rate of Si with C12 gas and XeF2 gas, and the 012 photoetching rate of a sample that was subjected to plasma treatment by changing the gas to CF4 without breaking the vacuum immediately after etching with CI2 or XeF2. It shows the photoetching speed. That is, the photo-etching rates of the two types without CF4 treatment are about 20 A/min and about 14 A/min, whereas the photo-etching rate of Si treated with CF4 is as high as about 100 A/min. That is, the Si surface exposed to halogen atoms such as CI2 and XeF2 is extremely easily oxidized and has a low photoetching rate. On the other hand, even if it contains halogen, like CF4, it also contains carbon, so its surface is extremely difficult to oxidize. That is, a high etching rate can be obtained by photoetching. Next, in the graph of the Auger analysis results in Figure 3, the photoetching time is within 2 minutes under these conditions, that is, as long as the carbon concentration is high.
When the oxygen concentration is low, the photo-etching time becomes long, and the Si surface begins to appear where the carbon concentration decreases, the oxygen concentration increases. From this, the layer containing carbon,
Resistant to oxidation, resulting in low temperature photo etching,
In a low-damage process, contamination layers can be removed without damaging the underlying Si substrate or the like.

In the above example, C12 gas was flowed while evacuating, and D
Although deep UV light was irradiated, the processing protection layer 15 and the contaminant layer 14 can be removed even if CI2 gas is introduced into the -tan chamber, evacuation is stopped, and deep UV is irradiated in a C12 atmosphere.

Furthermore, CI2 gas is introduced into the chamber and adsorbed to the sample surface! : Exhaust C12 gas and add De to this adsorbed gas.
You may irradiate with epUV. In this case, although the etching rate decreases, the controllability of the etching rate becomes better.

(Effects of the Invention) The method of forming the surface treatment protective layer of the present invention and removing it by photo-etching as necessary, that is,
Even when exposed to the outside air, a surface was obtained on which no surface oxide film was formed. This effect is due to the Auge effect in Fig. 3 mentioned earlier.
This was sufficiently confirmed from the r-analysis results and the photo-etching results shown in Table 1.

In addition, this method can naturally be used as a surface protective film before crystal growth, and due to low temperature and low damage, a sample surface free of carbon and other impurities can be obtained, making it possible to obtain a sample surface free of carbon and other impurities, which is superior to the natural oxide film used in conventional technology in semiconductor processes, etc. Completely improved the major problem of removal.

[Brief explanation of the drawing]

FIGS. 1(a) to (c) are schematic cross-sectional views showing one embodiment of the present invention, FIG. 2 is a diagram showing the dependence of Si etching rate on 012 pressure, and FIG. 3 is a diagram showing the effects of the present invention. FIG. 3 is a diagram of Auger analysis results showing how impurities such as carbon are removed. 11...Resist mask, 12...5i0213.
...Si substrate, 14... Contamination layer Fig. 1 14 Contamination layer (a) (C) O 2 Fig. CfL2 pressure (Torr)

Claims (1)

[Claims] Immediately after the dry etching or dry film forming process, and before exposing the sample to the outside air, halocarbon gas or a gas containing it is discharged to form a surface protective film, and D
A method for protecting a surface, which comprises introducing a gas that can be decomposed by deep UV light and etching the surface protective film, removing the surface protective film by irradiating it with deep UV light, and then performing the next step in a vacuum.