JPH01212438A - Dry etching process - Google Patents

Abstract

PURPOSE:To enable Si to be etched efficiently in high anisotropy subjected to sufficient selection ratio to SiO2 by using a gas mainly comprising C2Cl3F3 as an etching gas. CONSTITUTION:C2Cl3F3 (trichlorotriphloroethyle, flon 113) is used as an etching gas while C2Cl3F6 is used as a cooling gas. Thus, Si can be etched efficiently and in high anisotropy subjected to sufficient selection ratio to SiO2 and photoresist, furthermore, C2Cl3F3 being applicable for non-industrial use as a refrigerant etc. can secure extremely safe operations while facilitating the application to mass production.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dry etching method, particularly a dry etching method using excitation means by electric discharge.
The present invention relates to a technique that is effective for forming circuit patterns in the manufacturing process of semiconductor devices.

[Conventional technology]

In the manufacturing process of semiconductor devices, dry etching methods for forming circuit patterns on a thin film material (so-called base) made of silicon (Si) that constitutes an integrated circuit can be classified into the following three types, focusing on the etching gas. Can be separated.

(1) Dry etching method using a gas partially containing chlorine (CI) (hereinafter referred to as CI-based dry etching method) Specific examples of the gas include CC1, 5iC14, PCl5
, BCIs, C1,, IC1, etc.

(2) Dry etching method using a gas containing at least a portion of bromine (Br) or iodine (1)
This is a dry etching method typified by the dry etching method described in Japanese Patent No. 8-100684.
As a specific example of the Br-based dry etching method, CB r Fs (+Ot)
+α, Cm Brg F4+α, and the like.

(3) Dry etching method using a gas partially containing fluorine (F) (hereinafter referred to as F-based dry etching method) Specific examples of the gas include SF, , CF, and Si
F, etc.

As an example of dry etching technology,
"Electronic Materials 198 November Special Edition" published by Kogyo Choshokai Co., Ltd., November 20, 1985, P119-P124
There is.

[Problem to be solved by the invention]

The inventors have discovered that the Ct-based, Br-based, and F-based dry etching methods have the following problems.

(1) In the CI-based dry etching method, for example, deep grooves (hereinafter referred to as U
When machining a U-groove), a sub-trench tends to form at the bottom of the U-groove, and from the viewpoint of safety in the working environment, it is not desirable to introduce it into a mass production factory.

(2) In the Br-based dry etching method, CB
Since rF5, Cm Brt Fa, etc. are gases with high boiling points, they are not allowed to enter the chamber and exhaust pump.

Depositions increase, reliability deteriorates, and the equipment is adversely affected.

(3) In the F-based dry etching method, the above (2)
) Not only does it have the same problem as F, but F is a gas that in principle performs equal etching! Therefore, if the flow rate ratio changes, the etched cross-sectional shape may change.

An object of the present invention is to provide a dry etching method that is suitable for mass production and has good etching characteristics.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Means for Solving CmH] Representative inventions disclosed in this application will be summarized as follows.

That is, trichlorotrifluoroethane is used as the main etching gas.

[Effect]

As a specific etching gas in the above means, Cz
When using a gas containing CIsFi as the main component, Sin
, and with sufficient selectivity to the photoresist.
SL can be etched efficiently and with strong anisotropy.

Since this Ct CIs Fs is a gas used commercially as a refrigerant, extremely safe scraping operation can be ensured, and it is easy to apply to mass production.

〔Example〕

FIG. 1 is a vertical cross-sectional view showing a dry etching device used in a dry etching method according to an embodiment of the present invention, FIGS. 2 and 3 are enlarged partial cross-sectional views for explaining its operation, and FIG. 4 to 8 are diagrams for explaining the operation.

In this embodiment, the dry etching apparatus is equipped with a chamber 3 that constitutes a processing chamber 2 for processing a wafer 1 as an object to be processed. It is formed from Belljar 5. The main body 4 is formed into a substantially cylindrical shape with closed upper and lower end surfaces, and a substantially central portion of the upper end wall is largely opened.

The bell jar 5 is formed into a hollow body shape of an approximately semicircular sphere,
It is removably placed over the main body 4 so as to close the central opening thereof, and is configured to be movable up and down relative to the main body 4. An exhaust port 6 for evacuating the inside of the processing chamber 2 is provided on the lower end wall of the main body 4, and the exhaust port 6 is fluidly connected to a vacuum exhaust system M (not shown) equipped with a high vacuum pump or the like. ing.

On the other hand, an etching gas supply path 8 for supplying an etching gas 7 as described later is arranged in an annular manner in the upper end wall opening of the main body 4, and this supply path 8 supplies the etching gas 7 all around. It is designed to blow out air as uniformly as possible. An etching gas supply source 9 is connected to this supply path 8 via a controller 10 consisting of a mass flow controller or the like.

A susceptor 11 for holding the wafer l is arranged concentrically inside the processing chamber 2, and the susceptor 11 is connected to the main body 4.
It is supported horizontally by a support shaft 12 vertically inserted from the lower end wall of the. The support shaft 12 is configured to move forward and backward relative to the main body 4, and by adjusting this movement, the height position of the susceptor 11' in the processing chamber 2 can be adjusted. Susceptor 11 and support shaft 12
A cooling gas flow path 13 is arranged and laid inside and outside of the processing chamber 2, and this flow path 13 supplies cooling gas supplied from a cooling gas supply source 14 connected to the cooling gas flow path 13 to the wafer 1 of the susceptor 11. By flowing to the back surface, the wafer 1 held on the susceptor 11 is cooled. A susceptor 11 is placed in the opening of the main body 4.
A high frequency power source (RF power source) 16 is electrically interposed between the electrode 15 and the support shaft 12.

A waveguide 17 is arranged to surround and cover the belljar 5 on the outside of the chamber 3, and a magnetron 18 is installed at the end of the waveguide 17 on the opposite side from the belljar 5. The magnetron 18 is configured to be able to irradiate the wafer 1 inside the bell jar 3 with microwaves 19 of a predetermined frequency as described later through the waveguide 17. A tuning 20 is interposed between the magnetron 18 and the belljar 5 of the waveguide 17, and a first coil 21 and a second coil 22 are provided at the end of the waveguide 17 on the belljar 5 side.
are arranged one above the other and are encased in an annular shape, and both coils are configured so that their coil currents can be adjusted independently of each other.

Next, an embodiment of the dry etching method according to the present invention will be described in connection with drilling a U-groove as shown in FIG. 2 using the dry etching apparatus having the above structure.

In Fig. 2, 31 is the base to be etched;
In this embodiment, the substrate of the wafer 1 itself or SiN formed on the wafer 1 is used. 32 is a masking layer deposited on the wafer 1, and in this embodiment is made of silicon dioxide (SjO,). 3
3 is a window hole opened in the masking layer 32, and a pattern is formed therein. 34 is the base 31 by etching.
This is a U-groove drilled in the groove, and the width of the groove is approximately 1 μm and the depth of the groove is approximately 5 μm.

The wafer 1 to be dry-etched is transferred onto the susceptor 11 and held in a down position with the bell jar 5 open relative to the main body 4.

When the main body 4 and the bell jar 5 are hermetically sealed, the processing chamber 2 is evacuated to a high degree of vacuum (IO-'Torr in this embodiment) through the exhaust port 6 by a vacuum exhaust device.

Etching gas 7 is supplied from an etching gas supply source 9 to a supply path 8 through a controller 10, and introduced from the supply path 8 into the processing chamber 2 as uniformly as possible throughout.

When the pressure in the processing chamber 2 stabilizes at a specified pressure, the microwave 19 is emitted by the magnetron 18 at a specified output and frequency (in this example, an output of 220 mA).
2.45 C; Hz) is transmitted through the belljar 5 and irradiated onto the wafer I on the susceptor I, and the coils 21 and 22 are excited.

On the other hand, a predetermined high frequency power (in this embodiment, output 1
00W, 13.56MHz) is applied.

As a result, a plasma atmosphere (plasma positive column) 23 is generated around the wafer 1 with extremely high density and effectiveness. At this time, cooling gas is being supplied from the cooling gas supply source 14 to the flow path 13, thereby cooling the wafer l.

Under the above conditions, the wafer I is etched by ion-assisted etching (reactive ion etching or reactive sputter etching), and as shown in FIG. will be established.

Here, in this example, as the etching gas,
ct c ti F2 (trichlorotrifluoroethane, referred to as Freon 113) is used, and Ct CIs Fs is also used as a cooling gas.

After etching is completed or after a preset time has elapsed,
Once the inside of processing chamber 2 is in a safe condition, Belljar 5
is opened relative to the main body 4, and the processed wafer l is lowered from above the susceptor 11 and sent to the next process such as a masking material removal process.

By the way, it is known that when plasma treatment is performed using Ct.Cl5Fa, the polymer is devodisilated by the CVD reaction. Therefore, C, C1, F
It has been predicted that if a simple dry etching process was attempted using the .

However, according to the inventor's experiments, using a microwave plasma dry etching device, the high frequency output was increased to 100%.
By setting the microwave output to about W and the microwave output to 200 W or more, it is possible to efficiently etch Si with a sufficient selectivity to 5 iOz without being hindered by the polymer's debodisilane, and with strong anisotropy. It was discovered that it can be done. This is considered to be due to the following reasons.

As shown in FIG. 3, radicals and ions such as C, CI, F, and CFx are generated by excitation, dissociation, and ionization of Cz CIs F* supplied to the plasma atmosphere 23. At this time, a dark space called an ion sheath region is generated between the plasma and the wafer, and ions are perpendicularly incident on the wafer surface due to a potential difference corresponding to the electric power applied by the high frequency power source 16. This performs anisotropic etching.

When F radicals reach the Si surface, volatile 5IFa
The etching progresses. By increasing the incident energy of ions (that is, the power applied by the high frequency power source 16), Si is etched quickly only in the ion irradiated area, so that anisotropic etching progresses. The progress of these anisotropic etching becomes more noticeable in the negative layer by increasing the microwave output.

Considering the case where F radicals or CFx ions are incident on the Stow surface, etching does not proceed easily when the F radicals reach the Stow surface because the 5i-O bond is more stable than the 5t-F bond. , when a CFx ion is incident, a stable C-0 bond is formed, which liberates Si in 5i02 and F of the CFx ion, and then a stable 5i-F bond is formed, resulting in a volatile The etching of SiO□ progresses as the temperature becomes 3iFa. However, when the high frequency output is set to around 100 W, the progress of etching of SiO is suppressed. Cz
Ionization rate and dissociation rate of C1s Fs, SiO of CFx
□This is thought to be because the adsorption rate to the surface is suppressed.

On the other hand, the reaction products in the plasma are St or stow.
The etched surface is etched, and a polymer layer 35 is formed on the etched surface by a polymerization reaction on the surface. However, as described above, since the etching to the Si surface proceeds with anisotropy in the vertical direction, the polymer layer 36 is etched on the bottom surface of the groove 34 before it is formed during the etching process. Therefore, the polymer layer 36 is formed only on the side wall surface of the U-groove 34, and the progress of etching in the vertical direction is further enhanced.

FIGS. 4 to 8 show the results of an experiment conducted by the present inventor using CI C1x F FIG. In both figures, the solid line curve shows the case of SS, the broken line curve shows the case of 5 loz, and the vertical axis shows the erasure gray (pm/min).

FIG. 4 is a diagram using high frequency output (W) as a parameter, and the experimental conditions were microwave output 220 mA, etching pressure IQmTorr, gas flow rate 883CCm,
It is.

According to FIG. 4, it is understood that the etching rate of 5 lOt increases from around 100 W of output.

FIG. 5 is a diagram using microwave output (W) as a parameter, and the experimental conditions were high frequency output too high, etching pressure 10 mTorr, and gas flow rate 883 CCm.

According to FIG. 5, it is understood that as the microwave output becomes higher, the etching rate of St increases, whereas the etching rate of 5iOz hardly changes.

Figure 6 is a diagram using etching pressure (mTorr) as a parameter, and the experimental conditions were high frequency output 100W, microwave output 200mA, and etching pressure 10mTorr.
, the gas flow rate was 883 CCm.

According to FIG. 6, it is understood that the highest selectivity can be obtained at 5 mTorr.

Figure 7 is a diagram using the temperature of the susceptor as a parameter, and the experimental conditions were a high frequency output of 100 W, a microwave output of 22
0mA, etching pressure 10mT.

rr, gas flow 188 SCCm.

According to FIG. 7, it is understood that the temperature change of the susceptor has almost no effect on the progress of etching.

FIG. 8 is a diagram in which the amount of oxygen (O) added to C, Ct3 F3 is used as a parameter, and the experimental conditions are the same as those in FIG. 7.

According to FIG. 8, it is understood that the etching rate of St can be increased by adding oxygen (0 or more).

However, observation of the experimental results has revealed that the addition of 02 deteriorates the processed shape of the bottom of the U-groove.

According to the embodiment described above, the following effects can be obtained.

(1) As etching gas, Ct C1s Fs
By using a gas mainly composed of
It can be etched with strong anisotropy, and since CtCIsFi is a gas commonly used as a refrigerant, extremely safe operation can be ensured and it can be easily applied to mass production.

(2) Since 51 can be etched with a sufficient selection ratio for SiOx, a sufficient margin for mass production can be set.

(3) Since adhesion of reaction products to the vacuum pump is suppressed, a decrease in the operating rate of the apparatus can be suppressed.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Not even.

For example, although a microwave plasma dry etching apparatus has been described as a dry etching apparatus, it is also possible to use a dry etching method capable of performing reactive sputtering or reactive ion etching.

As the etching gas, not only CtCIsFi but also chlorofluorocarbons containing 3 chlorine atoms can be used.
A hydrocarbon compound having the above number of fluorine atoms and having 2 or more fluorine atoms may be used.

Since there are a large number of parameters that determine the processing performance of the dry etching method, it is desirable to consider not only the items listed in the above embodiments but also other items as appropriate.

The above explanation has mainly been about the case where the invention made by the present inventor is applied to the dry etching technology for Si, which is the field of application that is the background of the invention.
The present invention is not limited thereto, and can be applied to all dry etching methods for other molecules and atoms.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

By using a gas containing CtCIsFi as the main component as the etching gas, it is possible to efficiently etch Si with a sufficient selectivity to Sing and with strong anisotropy.
Since Fs is a gas used commercially as a refrigerant,
In addition to ensuring extremely safe operations,
Easy to apply to mass production.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a dry etching device used in a dry etching method according to an embodiment of the present invention; FIGS. 2 and 3 are enlarged partial cross-sectional views for explaining its operation; FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are diagrams for explaining the operation. 1... Wafer (workpiece), 2... Processing chamber, 3...
・Chi □ Yamba, 4...Main body, 5...Bellja, 6
...Exhaust port, 7...Etching gas (cz CIS
F! ), 8... Supply path, 9... Etching gas supply source, 10... Controller, 11... Susceptor, 12... Support shaft, 13... Distribution path, 14... Cooling supply Source, 15... Electrode, 16... High frequency power supply, 17
...Waveguide, 18...Magnetron, 19...Microwave, 20...Tuning, 21.22...
Coil, 31... Base, 32... Masking layer, 3
3... Window hole, 34... U groove, 35... Debodisilane layer. Agent Patent Attorney Tatsuya Kajihara R114 output (
W) Figure 5 H wave output (W) Figure 6 Craftsmanship, 1 move ship five power (sTory)

Claims (1)

[Claims] 1. Among hydrocarbon compounds substituted with chlorine and fluorine, those containing 3 or more chlorine and 2 or more fluorine are used as the main gas for the etching gas. A dry etching method characterized by: 2. The dry etching method according to claim 1, wherein trichlorotrifluoroethane is used as the etching gas. 3. The dry etching method according to claim 1, wherein a microwave plasma etching device is used.