Photoactivated composition for etching silicon nitride films. RU patent 2507219.

FIELD: chemistry.

SUBSTANCE: invention relates to production of integrated microcircuits and other electronic devices which use a plenary manufacturing technique based on photolithographic processes. The photoactivated composition contains a polymer base and a photosensitive component. The polymer base is polymethyl methacrylate and the photosensitive component is ammonium fluoride. The composition further contains a protophilic reagent - α-naphthylamine and solvents - acetone and trifluoroacetic acid. Components are in the following ratio, wt %: polymethyl methacrylate - 11.8; ammonium fluoride - 4.7-7.1; α-naphthylamine - 18.3; acetone - 8.3-10.7; trifluoroacetic acid - 54.5. Use of the composition simplifies the technological process of obtaining photoetched pattern in a silicon layer, while excluding development, baking and wet chemical etching steps.

EFFECT: simple technological process when using the disclosed composition also considerably reduces defects in the obtained articles.

3 ex

The invention relates to the field of microelectronics, in particular for the production of integrated circuits and other electronic devices using planar technology, based on processes. Getting a picture of an integrated circuit is by alternating many stages, with the participation of a large number of alternating layers of different purpose and corrosive environments, that is a source of great technological losses.

As dielectric mask layers when you create a picture of the electronic circuit typically use silicon dioxide SiO2 and silicon nitride. Chemical etching of silicon nitride in Windows picture presented many challenges. Usually it is done in a concentrated H 3 PO 4 when heated to 180 C, or in a mixture of concentrated acids (H 3 PO 4 +HF) with small speeds 10-15 nm/min (S. Moreau. . M: Mir, 1990, part 2, .886).

In such tough conditions, organic resists collapse, and the underlying layer of silicon etched. Plasma etching of silicon nitride spend plasma fluorinated hydrocarbons (CF 4 , CHF 3 C 2 F 6 and others). This can include Express erosion and radiation damage and heating of the substrate (a A.L. Plasmachemical processes and devices. - M: Chemistry, 1989. - 304 C.).

There is a method of highly selective etching of silicon nitride relatively silicon and silicon dioxide (Kastenmeier ..., Matsuo P.J., Oehrlein G.S. // J. Vac. Sci. And Technol. A. - 1999. and 17.6. - C.3179-3184).

Etching was carried out in plasma O 2 /N 2 , to which was added a small amount of f-gas (CF 4 or NF 3 ). Speed etching of silicon nitride when using a CF 4 was 30 nm/min and selectivity regarding the silicon up to 40 under conditions of full lack of etching of silicon dioxide. In the case of NF 3 etching rate reached 50 nm/min and selectivity etching relatively silicon and silicon dioxide - 100 and 70 respectively.

There is a method of etching of silicon nitride films in plasma CF 4 /O 2 with the addition of hydrogen-containing gases (Kataoka Yoshinori, Saito Shuichi, Omiya Kayoko // J. Electrochem. Soc. - 1999. - 146.9. - C.3435 - 3439. - English).

As of hydrogen-containing compounds used hydrogen, water and methanol. It is shown that the introduction of these gases in the plasma significantly increases the speed of etching of silicon nitride. The mechanism of the increase is related to the interaction of hydrogen with nitrogen atoms in the film with the formation of nitride NH 3 , which is removed from the surface.

The disadvantage of this method is the use of high-frequency plasma that requires expensive equipment and technology.

Known new technology photolithography without phase of manifestation for etching of silicon nitride (Hong Xiaoyin, Duan Shengquan, Lu Jianping, Wang Peiqing, Chen Yongqi // J. Vac. Sci. And Technol. B. - 1999. of 17.5. - C.2084-2089. - English).

Etching of silicon nitride was conducted in a gaseous mixture of H 2 O/HF/N 2 after the preliminary and UV irradiation (45-60 C). As a photoresist used poly() with the addition of the catalyst, which is used peroxidates of pen connection, tertiary amines and 5-. In this way, chosen as a prototype, you can create a positive figure of silicon nitride under exposed areas . The disadvantage of the proposed technology is picture, limited depth of etching material, as well as the use of corrosive gaseous environment.

The aim of the invention is development of songs for etching of silicon nitride films in photolithography processes, Si 3 N 4 without holding stages of manifestation, and chemical etching.

Using the specified composition will lead to a simplification of the production cycle the picture in silicon layer and therefore greatly reduce the number of defects of the products obtained.

The problem is solved by the fact that, as in the prototype, composition for etching of silicon nitride films includes polymer base and catalyst, but unlike the prototype as a polymer base composition contains polymethylmethacrylate PMMA, and as a catalyst α , which is a substance expressed properties, and additionally contains a photosensitive component, the ammonium fluoride and solvents acetone and acid at the following ratio of components, mass%:

Polymethylmethacrylate

Ammonium fluoride

α

acid

The claimed invention was as follows.

For the preparation of compositions for etching all components take in mass ratios presented in the formula of the invention. For this purpose prepare A solution: take a weighed portion of poly (methyl methacrylate) PMMA (0.50 g) and pour acetone (5.0 ml). Mix carefully mix with a glass rod and incubated for 24 hours before full dissolution of PMMA.

After the complete dissolution of PMMA in the solution of A being a 0.77 (g) and again stirred it with a glass rod (solution B). The complete dissolution of naphthylamine 30 minutes.

For preparation of a solution In is weighed on the scales (0.2-0.3 g) of ammonium fluoride NH 4 F and pour acid CF 3 COOH (1.5 ml), mix thoroughly. There is heating of the mixture, in 3-5 minutes is the complete dissolution NH 4 F.

Cooked solution B poured to a solution In and mix. This also happens a small system heating and increases the viscosity of the solution. The resulting composition for etching maintain within 1-2 hours before full dissolution of all components. The stated composition for etching of silicon dioxide films after cooking retains its properties for months at a temperature of 25 C.

The following examples illustrate the invention.

Example 1

The silicon plate with a layer of Si 3 N 4 , thickness of 0.21 microns, pre-purified from impurities in ethyl alcohol, put a pipette 1 drop compositions, prepared as follows. At first prepare A solution: take a sample of polymethyl methacrylate PMMA 0.5 g and fill in a 5 ml of acetone Mix carefully mix with a glass rod and incubated for 24 hours before full dissolution of PMMA.

Later in the solution And injected of 0.77 g and again stirred it with a glass rod (solution B). The complete dissolution of naphthylamine 30 minutes.

For preparation of a solution In is weighed on the scales (0.20 g) of ammonium fluoride NH 4 F and pour acid CF 3 COOH (1.5 ml), mix thoroughly. There is heating of the mixture, in 3-5 minutes is the complete dissolution NH 4 F.

Cooked solution B poured to the solution In the mixing received composition maintain within 1-2 hours before full dissolution of all components.

Then the plate is exposed under the lamp DRL-250 to full bleed film silicon nitride (30 min), irradiated spot wash with acetone with a cotton swab, watching the complete removal Si 3 N 4 .

Speed photochemical etching is 0,007 micron/min

Simultaneously determine the speed of the chemical etching, going without UV-irradiation within 30 minutes Chemical etching was observed. In the future, the contribution of this component was not taken into account.

Example 2

The silicon plate with a layer of Si 3 N 4 , thickness of 0.21 microns, pre-purified from impurities in ethyl alcohol, put a method of irrigation 3 ml songs for etching, prepared as follows. At first prepare A solution: take a sample of polymethyl methacrylate PMMA 0.50 g and pour acetone ml to 5.0 mix carefully Mix with a glass rod and incubated for 24 hours before full dissolution of PMMA.

After the complete dissolution of PMMA in the solution And injected of 0.77 g and again stirred it with a glass rod (solution B). The complete dissolution of naphthylamine 30 minutes.

For preparation of a solution In is weighed on the scales (0.30 g) of ammonium fluoride NH 4 F and pour acid CF 3 COOH (1.5 ml), mix thoroughly. There is heating of the mixture, in 3-5 minutes is the complete dissolution NH 4 F.

Cooked solution B poured to the solution In the mixing received song for photoetching maintain within 1-2 hours before full dissolution of all components.

Then the plate is exposed under the lamp DRL-250 for 20 minutes, irradiated spot wash with acetone with a cotton swab, watching the complete removal Si 3 N 4 .

Speed photochemical etching is 0.01 micron/min

Example 3

The silicon plate with a layer of Si 3 N 4 , thick 0,085 microns, pre-purified from impurities in ethyl alcohol, put a pipette 1 drop compositions, prepared as follows. At first prepare A solution: take a sample of polymethyl methacrylate PMMA 0.5 g and fill in a 5 ml of acetone mix carefully Mix with a glass rod and incubated for 24 hours before full dissolution of PMMA.

After the complete dissolution of PMMA in the solution And injected of 0.77 g and again stirred it with a glass rod (solution B). The complete dissolution of naphthylamine 30 minutes.

For preparation of a solution In is weighed on the scales (0.30 g) of ammonium fluoride NH 4 F and pour acid CF 3 COOH (1.5 ml), mix thoroughly. There is heating of the mixture, in 3-5 minutes is the complete dissolution NH 4 F.

Cooked solution B poured to the solution In the mixing received song for photoetching maintain within 1-2 hours before full dissolution of all components.

Then the plate is exposed under the lamp DRL-250 to full bleed film silicon nitride (5 min), irradiated spot wash with acetone with a cotton swab, watching the complete removal Si 3 N 4 .

Speed photochemical etching is 0.017 microns/min Advantage of the claimed invention is that when using systems for etching of silicon nitride films in photolithography potential for considerable contribution to the improvement of the planar technology by reducing the number of stages in the process of photolithography one cycle. While completely excluded stage of manifestation, and etching, which account for the largest number of defects and distortion of the picture schemes. Etching of silicon nitride and destruction of etching products takes place at the stage of the exposure. In addition exclude the use in the production of developers and etching agents on the basis of HF and H 3 PO 4 and disposal of waste. Eliminates the use of gas mixtures. In addition, in contrast to the prototype, nitride films on all thickness of a layer of silicon. Thus, the method of photoetching using the stated composition is potentially more efficient technology of microelectronics.

composition for etching of silicon nitride films, including polymer base and photosensitive component characterized by the fact that as a polymer base composition contains polymethylmethacrylate, as photosensitive component, the ammonium fluoride and additionally contains reagent - alpha- and solvents acetone and acid with the following component ratio, mass%:

polymethylmethacrylate

ammonium fluoride

α

acid