JPH0823073B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a dry etching method for a film of silicon or a silicon compound formed on the surface of a substrate, and more specifically, using a combination of specific compounds as a plasma generating gas. The present invention relates to a method of performing dry etching that enables even more etching control.

(Prior Art) Conventionally, dry etching techniques such as plasma etching, sputtering etching, reactive ion etching (RIE), and ion beam etching have been widely used in the production of electronic devices such as integrated circuits. Compared with the wet etching technique such as the solution method, this dry etching technique has advantages such as excellent microfabrication, reproducibility and controllability, easy process simplification, automation, and very few pollution problems. However, in addition to requiring special equipment for each, a new etching process is used to fully exhibit the characteristics of each device by making full use of the etching parameters that control the gas selection for plasma generation and the etching properties of each device. Need to develop.

Carbon tetrafluoride (CF ₄ ) containing a few percent of oxygen gas is generally used for etching silicon compounds, particularly polysilicon which is important in LSI. This etching gas is 2
It has a high etch rate of 50-500 nm and is excellent in terms of selectivity, handleability, and safety, so it is still widely used, but this mixed gas etching is isotropic etching. The side etch amount after etching is large, and it is substantially unsuitable for etching with a pattern width of 3 μm or less, and cannot be used in a process for forming a highly precise fine pattern. Moreover, by using a mixed gas of dichlorotetrafluoroethane (C ₂ Cl ₂ F ₄ ) which is an anisotropic gas and sulfur hexafluoride (SF ₆ ) which is an isotropic gas, side etching can be performed. It has been reported to reduce the amount.

(Problems to be Solved by the Invention) Dichlorotetrafluoroethane (C ₂ Cl ₂ F ₄ ) described above
There is no problem in etching a pattern width of up to 1 μm when a mixed gas of Fluorine and sulfur hexafluoride (SF ₆ ) is used, but dichlorolotetrafluoroethane ( Since it is necessary to increase the mixing ratio of C ₂ Cl ₂ F ₄ ) extremely, as a result, the etching rate is sacrificed and the throughput is lowered, which is not a practical process. As described above, since the anisotropic etching rates are contradictory in any case, development of an etching process having both properties is strongly desired.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a monolithifluoroethane (C ₂ Cl ₂₎ as a gas for plasma generation during dry etching of silicon or a silicon compound formed on a substrate surface. A gas was used in which F ₄ ) and sulfur hexafluoride (SF ₆ ) were mixed at a volume ratio of 5:95 to 95: 5.

(Function) Monochlorodifluoroethane contained in the mixed gas makes the etching anisotropic, and sulfur hexafluoride contained in the mixed gas increases the etching rate.

(Example) Below, the Example of this invention is described based on an accompanying drawing. Here, as the dry etching apparatus used for carrying out the present invention, for example, a parallel plate electrode plasma etching apparatus, a reactive ion etching apparatus or a microwave plasma processing apparatus such as ECR is suitable. It will be described with reference to FIG.

That is, in the microwave plasma processing apparatus, a metal case (2) is placed on a bottom plate (1), and a bell jar type (bell-shaped) quartz chamber (3) is provided in the case. A mixed gas inlet pipe (4) is connected to the upper part of the chamber (3), and an opening (5) and a hole (6) connected to a vacuuming device are formed in the bottom plate (1), and the opening (5) is formed.
The table (7) on which the substrate (W) is placed is fitted in the table. Here, the table (7) is movable up and down, receives the substrate (W) at a position lowered from the position shown in FIG. 1, and ascends to close the opening (5) in an airtight manner and into the chamber (3). Face the substrate (W).

On the other hand, a microwave oscillator (8) is arranged at a position separated from the case (2), and the oscillator (8) and the upper surface of the case (2) are flexible coaxial cables (9) as a substitute for a waveguide. The antenna (10) facing the inside of the case is attached to the copper wire forming the center of the coaxial cable (9), and the magnetic field generating coil (11) is arranged outside the case (2).

In the above, the table (7) is lowered, the substrate (W) is placed on the upper surface of the table (7), and then the table (7) is raised to hermetically close the opening (5) of the bottom plate (1). , 1T inside the chamber (3) through the hole (6)
The microwave generated by the oscillator (8) is introduced into the case (2) through the coaxial cable (9) while the pressure is reduced to orr or less and the mixed gas is introduced from the introduction pipe (4) into the chamber (3). To transmit. Then, the mixed gas introduced into the chamber (3) is discharge-excited to generate plasma, and the thin film-like object to be etched formed on the surface of the substrate (W) is etched by the plasma.

Here, the material to be etched is, for example, silicon or a silicon compound, and examples of such a material include single crystal or polycrystalline silicon, silicon oxide, and the like, and those doped with impurities. Is also included. These objects to be etched are formed into a film on the surface of the substrate by a generally known method.

A mixed gas of monochlorodifluoromethane (CHClF ₂ ) and sulfur hexafluoride (SF ₆ ) is used as the mixed gas for plasma generation.

Here, FIG. 2 is an enlarged sectional view of the etched substrate,
Figure 3 shows the volume ratio of the mixed gas and side etching (S.
It is a graph showing the relationship with E), and the side etching (SE) amount is the dimension (L) from the hem to the hem of the resist pattern (R) and the upper part of the etched substrate (W) as shown in FIG. The difference (SE = L-1) from the dimension (1) is shown.

As is clear from these figures, the mixing ratio of monochlorodifluoromethane (CHClF ₂ ) and sulfur hexafluoride (SF ₆ ) should be in the range of 5:95 to 95: 5 by volume. That is, when the ratio of sulfur hexafluoride (SF ₆ ) exceeds 95% by volume (the ratio of monochlorodifluoromethane (CHClF ₂ ) becomes less than 5% by volume), the side etching amount is increased due to the strong isotropic etching. When the ratio of monochlorodifluoromethane (CHClF ₂ ) exceeds 95% by volume (the ratio of sulfur hexafluoride (SF ₆ ) becomes less than 5% by volume), the etching capacity is increased in the middle of the night. Therefore, it takes a long time to complete the target etching. And a particularly preferable mixing ratio is 30:70 to 70:
It can be said that the range is 30.

 Next, specific examples and comparative examples will be described.

Example 1 Film thickness of 410 mm formed on the surface of a silicon substrate having a diameter of 100 mm
A 0.8 μm line width pattern of a positive resist TSMR-8800 (made by Tokyo Ohka Kogyo Co., Ltd.) on the phosphorus-doped polysilicon film of
Microwave plasma processing equipment TSME-53
Using 00 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), dry etching was performed using a mixed gas of CHClF ₂ and SF _{6 with} a volume ratio of 2: 1 as a reaction gas. The processing conditions at that time were 6.5 × 10 ⁻³ Torr, the microwave output was 100 W, and the bias output was 100 W. The etching time was 45 seconds, and the etching rate was calculated from the residual film at that time to find that it was 320 nm and the uniformity was ± 1.1%. Further, the side etch amount under that condition was 0.05 μm, and a highly precise fine pattern with substantially no undercut was obtained.

Comparative Example 1 A positive resist pattern similar to that of Example 1 was used, and the same apparatus was used as a reaction gas containing C ₂ Cl ₂ F ₄
When mixed with SF _{6 at} a volume ratio of 2: 1 and treated under the same conditions as in Example 1, the etch rate was 330 nm. The uniformity was ± 3.1%, and the side etch amount was 0.12 μm.

Example 2 A plasma etching apparatus OAPM-400 was used, in which a positive resist pattern similar to that in Example 1 was formed.
(Manufactured by Tokyo Ohka Kogyo Co., Ltd.) and CHClF _{2 as} the reaction gas
SF ₆ was mixed at a volume ratio of 1: 1 and dry etching was performed. The processing condition at that time is 0.15 Torr and output is 50W. At this time, the etch rate was 340 nm, the uniformity was ± 3.5%, and the side etch amount was 0.09 μm.

Comparative Example 2 Using the same positive type resist pattern as in Example 1 and using the same apparatus as in Example 2, C ₂ ClF ₅
When SF ₆ was mixed at a volume ratio of 2: 1 and treated under the same conditions as in Example 2, the etch rate was 270 nm, the uniformity was ± 3.1%, and the side etch amount was 0.14 μm. .

Each example described above will be described. In Example 1 and Comparative Example 1, a microwave plasma treatment apparatus was used, and the reaction gas was a combination of CHClF ₂ and SF _{6 in} the example, and C in the comparative example.
Processing was performed under the same conditions using a combination of ₂ Cl ₂ F ₄ and SF ₆ , and the side etch amounts of each were compared. As a result, there was no difference in the etch rate, but the side etch amount was improved by 0.07 μm.
The line width of the m pattern is unexpectedly improved.
Further, in the comparison between Example 2 and Comparative Example 2, a plasma etching apparatus was used, and CHClF ₂ was used as the gas in the Example.
SF ₆ was mixed at a volume ratio of 1: 1 and SF of C ₂ ClF ₅ was used in the comparative example.
₆ were mixed at a volume ratio of 2: 1 and treated under the same conditions. As a result, in the comparative example, the side etch amount was increased by 0.05 μm as compared with the example, even though a large amount of C ₂ ClF ₅ , which is an anisotropic gas, was mixed. By comparing each of these, CHClF ₂ was used as the gas for plasma generation.
By combining SF ₆ , it is possible to finish the pattern shift amount after etching to an extremely small amount, and it is 1 μm.
It can be said that the etching process is sufficiently applicable to etching of the following pattern widths.

(Effects of the Invention) As described above, according to the present invention, in dry etching of a fine pattern of a silicon compound such as polysilicon or silicon nitride, generally, anisotropic etching reduces the etching rate, and therefore, Despite the limitations of the etching process, such as a decrease in the selectivity with, sulfur hexafluoride selected from reactive gases with a large etch rate as a mixed gas and a reaction that improves anisotropy Since monochlorodifluoromethane selected from the organic gases is combined in a specific range ratio, it is possible to perform etching having both good anisotropic etching and good etching rate.

Therefore, according to the present invention, anisotropic dry etching can be performed on a coating of a silicon compound such as polysilicon or silicon nitride formed on a silicon substrate at a high speed and without substantially forming an undercut. Therefore, a high-precision fine pattern can be easily formed.

[Brief description of drawings]

FIG. 1 is a view showing an example of a processing apparatus used for carrying out the method of the present invention, FIG. 2 is an enlarged sectional view of an etched substrate,
FIG. 3 is a graph showing the relationship between the mixing ratio of the mixed gas and the side etching amount. In the drawing, (3) is a chamber, (4) is a mixed gas introduction pipe, (7) is a table, and (W) is a substrate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Muneo Nakayama 4-28-2 Shirota, Setagaya-ku, Tokyo (56) Reference JP-A-51-27833 (JP, A) JP-A-61-131456 (JP, A)

Claims (1)

[Claims] 1. A method of dry-etching silicon or a silicon compound formed on a substrate surface, wherein monochlorodifluoromethane (CHClF ₂ ) and sulfur hexafluoride (SF ₆ ) are used as plasma generating gas for dry etching.
A dry etching method characterized by using a gas in which and are mixed in a volume ratio of 5:95 to 95: 5.