JPS62125627A - Removing method for organic film - Google Patents

Abstract

PURPOSE:To remove an organic film formed on a substrate in a short time by exposing the film formed on the substrate made of an inorganic material with active gas formed by the plasma of a specific mixture gas to decompose and vaporize the film. CONSTITUTION:1-10vol% of C3F8, C4F8, C4F10, C5F12 and oxygen gas are mixed, a plasma is generated in the mixture gas as an active gas, and an organic film formed on a substrate is exposed with the active gas to remove the film in a short time without damaging the substrate. C3F8, C4F8, C4F10, C5F12 may be used independently, and may also be used in mixture. The volumetric ratio to oxygen is 1-10%, and preferably 3-5%, pressure of mixture gas is preferably 0.1-100Torr, and 0.5-3.0Torr as an optimum range. Thus, the film formed on the substrate made of an inorganic material such as a silicon wafer can be removed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for removing an organic film formed on a substrate by decomposing and vaporizing it using an active gas turned into plasma.

(Prior Art) Removal of organic films formed on the surface of a substrate is performed in various fields such as the manufacturing process of semiconductor integrated circuits.

In the manufacture of semiconductor devices, organic films on semiconductor substrates are used as photoresists or organic insulator films, and are removed after use.

Conventionally, the main methods for such removal have been to dissolve and remove with strong acids or organic solvents.
Since large amounts of chemicals such as strong acids, strong bases, and organic solvents are used in the cleaning process, there are problems with the working environment and waste odors, so currently drying using plasma is the mainstream. .

In this plasma-based method, a substrate (silicon wafer) with an organic film formed on its surface is placed in a chamber.
Oxygen gas is introduced into this chamber under reduced pressure conditions (50 to 2 ooPa), and a high frequency voltage is applied to the electrode attached to this chamber (500 to 800 W) to generate plasma, and the main chain of the organic film is destroyed by this active species. It is designed to remove vaporization (CO2, Go, H2O) by cutting.

In addition to oxygen gas alone, freon (CF) is added to oxygen gas.
A method of removing 4) using a mixed gas is also disclosed in JP-A-5
It is known as No. 2-1131Ei4.

(Problems to be Solved by the Invention) However, when conventional plasma is used to remove an organic film, it takes 30 to 40 minutes to remove a photoresist film with a thickness of about lpm, and it takes a long time to remove a silicon wafer. There is a problem with etching itself and causing damage.

Further, even in a method using a mixed gas of oxygen gas and Freon, the expected ashing rate cannot be obtained, and the selectivity between the organic film and the substrate is small, resulting in damage to the substrate.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides 1 to 10% by volume of C3.
FB, C4FB, C4FIO, C5F12
By mixing oxygen and oxygen gas, turning this mixed gas into plasma and making it an active gas, and exposing the organic film formed on the substrate surface to this active gas, the organic film can be removed in a short time and without damaging the substrate. I decided to do so.

Here (, I FB , C4Fe , C4FIO+
C5F12 may be used alone or in combination.

(Example) Examples of the present invention will be described below based on specific numerical values.

[Example 1] A positive photoresist with a thickness of 1.2 gm was prepared using a parallel plate plasma device (OAPM-400: manufactured by Tokyo Ohka Kogyo ■).
- (OFPR-800: manufactured by Tokyo Ohka Kogyo ■) on its surface, a 5-inch silicon wafer is placed in a plasma reaction chamber, and this plasma reaction chamber contains 5% by volume of C3Fs gas. A mixed gas with oxygen gas was introduced and the pressure was reduced to 106 P,a (0.8 Torr), and a high frequency output of 250 W was applied to generate plasma in the reaction chamber to create an active gas atmosphere.

The photoresist then began to be ashed and was completely removed after one minute. The ashing rate of the photoresist at this time was 1.2 gm/min. The selectivity (etching rate ratio) between silicon oxide (SiO2) and photoresist was [200].

On the other hand, when photoresist was ashed using only oxygen gas and the other conditions were the same, the photoresist ashing rate was 0.21 Lm/sin. [Example 2] Same device as Example 1 1.21Lm thick positive photoresist) (OFPR-800: manufactured by Tokyo Ohka Kogyo ■)
A 5-inch silicon wafer with a surface formed on the surface was set in a plasma reaction chamber, and a mixed gas containing 3% by volume of C4F8 gas and oxygen gas was introduced into the plasma reaction chamber to generate a temperature of 106 F, a. (0.8 Tor
The pressure was reduced to r), a high frequency of 250 W was applied, and plasma was generated in the reaction chamber to create an active gas atmosphere.

Then, the photoresist begins to be ashed, and 1, 8
It was completely removed at an ashing rate of gm/1 Ilin. At this time, the selectivity ratio between the photoresist and the oxide film (Si02) was 130:1.

The results of the following examples conducted under varying conditions are shown in FIGS. 1 and 2.

From this result, it was found that by mixing both C3FB and C4FB with oxygen gas, the specific bearing time can be shortened compared to the conventional method, and the selectivity with respect to the substrate can be increased. The optimum volume ratio for oxygen is 1 to 10%, preferably 3 to 5%.

In addition, the pressure of the mixed gas is 0.1 to 100 Torr.
It is preferable to set it in the range of 0.5 to 0.5 as the optimal range.
3.0 Torr.

Furthermore, although silicon oxide was used as the substrate in the following examples, similar results were obtained with aluminum, silicon nitride, molybdenum silicide, tungsten silicide, tantalum, and the like. In addition, although only the ashing process was explained in the examples, the method of the present invention can also be applied as a so-called cleaning process to remove the residue after removing the organic film on the surface of the substrate using an organic solvent or the like. Of course.

(Effects of the Invention) As explained above, according to the method of the present invention, an organic film formed on the surface of an inorganic substrate such as a silicon wafer can be removed in a short time, and the method has extremely high productivity. In addition, there is less damage to the base, so L S,
It is extremely effective when applied to the manufacturing process of semiconductor integrated circuits such as I, ultra-LS, I, etc.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the mixing ratio of C3F8 and C4F8 and the ashing speed. Figure 2 shows C3F8 and C4
3 is a graph showing the relationship between the mixing ratio of F8 gas and the etching ratio. Patent applicant Agent: Tokyo Denshi Kagaku Co., Ltd.
Patent attorney F 1) Department of patent attorney
Kuni Ohashi Otoma Patent Attorney
Udo Koyama Patent Attorney No F
TI Shigeru○ 5 10
15 mixed system 8 (%) Saikontomi] Ina (0n)

Claims (1)

[Claims] 1-10% by volume C_3F_8, C_4F_8, C_4
A method for removing an organic film, in which the organic film formed on the surface of an inorganic substrate is exposed to an active gas made by turning a mixed gas of F_1_0, C_5F_1_2 and oxygen gas into plasma, and the organic film is decomposed and vaporized.