Etching composition for silicon nitride film

Abstract

The present invention relates to an etching composition for selectively etching a silicon nitride layer. The etching composition includes an inorganic acid, an epoxy-based silicon compound, and water. The etching composition of the present invention selectively removes a silicon nitride layer while minimizing damage to an underlying metal layer and preventing a silicon oxide layer from being etched.

Claims

1. An etching composition for a silicon nitride layer, the composition comprising an inorganic acid, an epoxy-based silicon compound, and water, wherein the composition comprises 80% to 90% by weight of the inorganic acid, 0.005% to 5% by weight of the epoxy-based silicon compound, and the water accounting for the remaining proportion.

2. The composition of claim 1, further comprising a fluorine compound.

3. The composition of claim 2, wherein the fluorine compound is selected from the group consisting of hydrogen fluoride, ammonium fluoride, ammonium hydrogen fluoride, or mixtures of two or more thereof.

4. The composition of claim 2, wherein the epoxy-based silicon compound is any one selected from the group consisting of gamma-Glycidoxymethyltrimethoxysilane, gamma-Glycidoxyethyltrimethoxysilane, gamma-Glycidoxypropyltrimethoxysilane, gamma-Glycidoxymethyltriethoxysilane, gamma-Glycidoxymethyltripropoxysilane, gamma-Glycidoxyethyltriethoxysilane, gamma-Glycidoxyethyltripropoxysilane, gamma-Glycidoxypropyltriethoxysilane, gamma-Glycidoxypropyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)methyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)propyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)methyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)methyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)propyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)propyltripropoxysilane, and mixtures of two or more thereof.

5. The composition of claim 2, wherein the inorganic acid is selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and mixtures of two or more thereof.

6. The composition of claim 2, wherein the epoxy-based silicon compound inhibits the silicon oxide layer from being etched at a temperature in a range of from 120° C. to 190° C.

7. The composition of claim 1, wherein the epoxy-based silicon compound is any one selected from the group consisting of gamma-Glycidoxymethyltrimethoxysilane, gamma-Glycidoxyethyltrimethoxysilane, gamma-Glycidoxypropyltrimethoxysilane, gamma-Glycidoxymethyltriethoxysilane, gamma-Glycidoxymethyltripropoxysilane, gamma-Glycidoxyethyltriethoxysilane, gamma-Glycidoxyethyltripropoxysilane, gamma-Glycidoxypropyltriethoxysilane, gamma-Glycidoxypropyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)methyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)propyltrimethoxysilane, beta-(3,4-Epoxycyclohexyl)methyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)methyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)ethyltripropoxysilane, beta-(3,4-Epoxycyclohexyl)propyltriethoxysilane, beta-(3,4-Epoxycyclohexyl)propyltripropoxysilane, and mixtures of two or more thereof.

8. The composition of claim 1, wherein the inorganic acid is selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and mixtures of two or more thereof.

9. The composition of claim 8, wherein the inorganic acid is phosphoric acid and sulfuric acid.

10. The composition of claim 1, wherein the epoxy-based silicon compound inhibits the silicon oxide layer from being etched at a temperature in a range of from 120° C. to 190° C.

11. The composition of claim 10, wherein the composition etches the silicon nitride layer at an etching rate that is 200 or more times higher than that of the silicon oxide layer at 160° C.

12. The composition of claim 11, wherein the composition etches the silicon nitride layer at an etching rate that is 1000 or more times higher than that of the silicon oxide layer.

Description

MODE FOR CARRYING OUT THE INVENTION

Examples 1 to 11

(1) For each of the compositions shown in Table 1 and Table 2, the components for each composition were introduced into an experimental beaker equipped with a magnetic bar according to the composition ratio therefor. The mixtures in the respective beakers were stirred at a speed of 500 rpm for 10 minutes at room temperature to prepare various compositions.

Comparative Examples 1 to 4

(2) Compositions were prepared in the same manner as in the examples according to the composition components and composition ratios shown in Table 1.

(3) TABLE-US-00001 TABLE 1 Composition Etching rate Inorganic Silicon (A/min.) acid compound Water Nitride Oxide Component Content Component Content Component Content layer layer Selectivity Example 1 A-1 85 B-1 0.01 C-1 remainder 92.3 0.3 308 Example 2 A-1 85 B-1 0.1 C-1 remainder 91.8 0.2 459 Example 3 A-1 85 B-1 0.5 C-1 remainder 91.5 0.1 915 Example 4 A-1 85 B-1 1 C-1 remainder 90.8 0.1 908 Example 5 A-1 85 B-2 0.2 C-1 remainder 91.6 0.2 458 Example 6 A-1 85 B-3 0.05 C-1 remainder 91.8 0.3 306 Example 7 A-1 85 B-4 0.3 C-1 remainder 90.9 0.2 455 Example 8 A-1 85 B-5 0.1 C-1 remainder 91.5 0.2 458 Example 9 A-1 85 B-6 0.5 C-1 remainder 91.3 0.1 913 Comparative A-1 85 B-1 0.001 C-1 remainder 92.5 0.9 103 Example 1 Comparative A-1 85 B-1 10 C-1 remainder 20.3 0.2 101 Example 2 Comparative A-1 85 B-7 0.1 C-1 remainder 90.3 1.4 65 Example 3 Comparative A-1 85 B-8 0.5 C-1 remainder 90.8 1.1 83 Example 4

(4) TABLE-US-00002 TABLE 2 Composition Etching rate Inorganic Silicon Fluorine (A/min.) acid compound Water compound Nitride Oxide Component Content Component Content Component Content Component Content layer layer Selectivity Example A-1 85 B-1 0.5 C-1 remainder — 0 91.5 0.1 915 3 Example A-1 85 B-1 0.5 C-1 remainder D-1 0.1 173.9 0.1 1739 10 Example A-1 85 B-1 0.5 C-1 remainder D-2 0.1 208.7 0.2 1044 11 A-1: phosphoric acid B-1: gamma-Glycidoxypropyltrimethoxysilane B-2: glycidoxyetyltriethoxysilane B-3: gamma-Glycidoxymethyltrimetoxysilane B-4: gamma-Glycidoxypropyltriprothoxysilane B-5: beta-(3,4-Epoxycyclohexyl)etyltrimethoxysilane) B-6: beta-(3,4-Epoxycyclohexyl)propyltrimethoxysilane) B-7: tetra ethly ortho silicate B-8: amino propyl triethoxy-silane C-1: deionized water D-1: ammonium fluoride (NH.sub.4F) D-2: hydrofluoric acid

(5) Characteristics Measurement (Measurement of Etching Rates of Silicon Oxide Layer and Silicon Nitride Layer)

(6) To measure the performance of each of the etching compositions prepared in the examples and the comparative examples, a silicon nitride layer and a silicon oxide layer were deposited on respective wafers using the same CVD method that is used in a semiconductor device manufacturing process, to prepare a silicon nitride wafer and a silicon oxide wafer.

(7) Before etching each of the layers, the initial thickness before etching was measured using a scanning electron microscope and an ellipsometer.

(8) Next, the etching process was performed by immersing the coupons of the silicon oxide wafer and the silicon nitride wafer in each etching composition maintained at 160° C. in a quartz stirring tank stirred at a speed of 500 rpm. After the etching was completed, each wafer was washed with ultrapure water, and the remaining etching composition and moisture were completely dried using a drying device.

(9) The thickness of each of the dried wafer coupons remaining after the etching was measured using a scanning electron microscope and an ellipsometer.

(10) The etching rate was measured on the basis of a change in the thickness of the thin layer before and after the etching.

(11) Referring to Table 1, the etching compositions of Examples 1 to 9 exhibit an excellent selective etching rate for a silicon nitride layer compared to that for a silicon oxide layer, which is achieved by suppressing the etching of the silicon oxide layer.

(12) From the results, it is confirmed that the etching composition of the present invention improves the etching rate, the etch selectivity, and the etching stability of a silicon nitride layer due to the presence of the epoxy-based silicon compound. That is, the present invention provides an etching composition capable of improving the efficiency of an etching process.

(13) Referring to Table 2, as in Examples 10 to 11, when the etching compositions in which an epoxy-based silicon compound serving as an etching inhibitor for a silicon oxide layer and a fluorine compound serving as an etching enhancer for a silicon nitride layer are both included are used, the etching rate of the silicon nitride layer is remarkably increased due to the addition of the fluorine compound but the etching rate of the silicon oxide layer hardly changes.

(14) Compared with Example 3 in which the fluorine compound was not used, the etching rate of the silicon nitride layer is increased by almost two or more times due to the action of the fluorine compound, but the etching rate of the oxide layer is just little changed due to the action of the silicon oxide layer etch inhibitor. Therefore, the effect of greatly improving the etch selectivity is obtained.

(15) Therefore, the etching composition of the present invention enables a high etching rate and a high selectivity when being used in a process of etching a silicon nitride layer, thereby being applicable to equipment for a single wafer process (SWP).

(16) Characteristics Measurement (Detection of Particles and Abnormal Growth of Silicon Oxide Layer)

(17) Reaction by-products generated by the etching composition may accumulate, thereby increasing the thickness of the layer on which the etching process is performed. This phenomenon is called abnormal growth. In addition, reaction by-products generated by the etching composition may generate particles. When the abnormal growth or particles occur, various defects may occur in the subsequent process.

(18) The surfaces of the silicon oxide layers etched in Comparative Examples 1 to 4 and Examples 1 to 11 were scanned with an electron microscope (SEM) to examine whether particles were generated, and the vertical cross-sections of the etched silicon oxide layers were photographed with an electron microscope (SEM). The results of testing for abnormal growth are shown in Table 3 below.

(19) TABLE-US-00003 TABLE 3 Presence/absence Presence/absence of particles of abnormal growth Example 1 X X Example 2 X X Example 3 X X Example 4 X X Example 5 X X Example 6 X X Example 7 X X Example 8 X X Example 9 X X Example 10 X X Example 11 X X Comparative Example 1 X ◯ Comparative Example 2 ◯ ◯ Comparative Example 3 ◯ ◯ Comparative Example 4 ◯ ◯

(20) When comparing Examples 1 to 11 with Comparative Examples, as shown in Table 3, neither particles nor abnormal growth occurred in the etching compositions of Examples 1 to 11 according to the present invention were used.

(21) In contrast, abnormal growth occurred when the etching composition of Comparative Example 1 was used, and both particles and abnormal growth occurred when the etching compositions of Comparative Examples 2 to 4 were used.

(22) In conclusion, the etching composition according to the present invention can reduce the occurrence of defects by minimizing particles and abnormal growth during an etching process.