WO2010086745A1

WO2010086745A1 - Method of etching lanthanum-containing oxide layers

Info

Publication number: WO2010086745A1
Application number: PCT/IB2010/000334
Authority: WO
Inventors: Robert Hsu (Ming-Ann); Prema Sonthalia; Chih-Long Chiang; Lillian Tang (Ching-Hsuan)
Original assignee: ATMI Taiwan Co Ltd
Current assignee: ATMI Taiwan Co Ltd
Priority date: 2009-02-02
Filing date: 2010-01-29
Publication date: 2010-08-05
Anticipated expiration: 2011-08-02
Also published as: TW201042718A; WO2010086745A8

Abstract

Lanthanum oxide or lanthanoid-containing oxides are etched from substrates intended for microelectronic devices using a buffered halide solution, the active ingredient preferably comprising, consisting or consisting essentially of a salt of the formula: [NR¹R²R³R⁴]⁺X^- wherein X = F, Cl, Br or I, and R¹, R², R³ and R⁴ may be the same or different from one another, and are selected from hydrogen, straight-chained C₁-C₆ alkyls, branched C₁-C₆ alkyls, substituted C₆-C₁₄ aryl, unsubstituted C₆-C₁₄ aryl, and combinations thereof. A fluoride-free active ingredient, e.g. ammonium chloride, is preferred. The pH is preferably in the range 3 to 6, and may be adjusted with a quaternary ammonium hydroxide such as tetramethylammonium hydroxide (TMAH). Contact times from about 5 seconds to about 10 minutes, at temperatures from about 5°C to about 60°C, are preferred. A passivating agent such as sorbitol, ethylene glycol, propylene glycol, glycerol or PEG may be used to reduce the etching rate.

Description

METHOD OF ETCHING LANTHANUM-CONTAINING OXIDE LAYERS

FIELD

[0001] The present invention relates generally to methods of etching lanthanum-containing oxide layers.

DESCRIPTION OF THE RELATED ART

[0002] As the semiconductor manufacturing industry pushes the limits of CMOS architecture to ever smaller physical dimensions, e.g., 45nm, 32 nm and 22 nm nodes, device makers are obliged to move away from common Silicon/Silicon dioxide (Si/SiO2) technology and integrate more new materials in the chips, such as high-k/metal gate (HKMG). [0003] Current CMOS technology includes the use of HK+MG stacks on hafnium-based high-k including a capping layer such as lanthanum oxide as the nMOS cap between the high- k material and the metal stack. Subsequent to deposition of the lanthanum oxide, patterning is performed to define the nMOS device regions. An etchant material is needed to controllably and predictably remove lanthanum oxide during the manufacturing process of the HK + MG stacks.

SUMMARY

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS THEREOF

[0004] The present invention generally relates to a method of etching lanthanum oxide and other lanthanoid-containing oxides from a microelectronic device. Preferably, the method removes excess lanthanum oxide and/or lanthanoid-containing oxide without damaging other materials present on the microelectronic device including, but not limited to, thermal oxide, polysilicon and the high-k material. [0005] "Microelectronic device" corresponds to semiconductor substrates, flat panel displays, phase change memory devices, solar panels and other products including solar substrates, photovoltaics, and microelectromechanical systems (MEMS), manufactured for use in microelectronic, integrated circuit, or computer chip applications. It is to be understood that the terms "microelectronic device," "microelectronic substrate" and "microelectronic device structure" are not meant to be limiting in any way and include any substrate or structure that will eventually become a microelectronic device or microelectronic assembly. The microelectronic device can be patterned, blanketed, a control and/or a test device. A "rejected microelectronic device" structure is intended to capture all microelectronic devices that can be reclaimed, reworked, and/or cleaned according to the methods of the invention.

[0006] "Substantially devoid" is defined herein as less than 2 wt. %, preferably less than 1 wt. %, more preferably less than 0.5 wt. %, and most preferably less than 0.1 wt. %, based on the total weight of the composition.

[0007] As used herein, "about" is intended to correspond to ± 5 % of the stated value. [0008] As defined herein, "lanthanoid-containing oxide" corresponds to oxides including at least one of the lanthanoid metals (previously known as the lanthanides) selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and any combination thereof. Specific examples include, but are not limited to, lanthanum oxide, lanthanum silicate, lanthanum aluminate, lanthanum borate, lanthanum hafnium oxide, lanthanum zirconium oxide, lanthanum lutetium oxide, and lanthanum erbium oxide. [0009] Compositions may be embodied in a wide variety of specific formulations, as hereinafter more fully described.

[0010] In all such compositions, wherein specific components of the composition are discussed in reference to weight percentage ranges including a zero lower limit, it will be understood that such components may be present or absent in various specific embodiments of the composition, and that in instances where such components are present, they may be present at concentrations as low as 1 ppm (part per million), based on the total weight of the composition in which such components are employed.

[0011] In general, a method of etching lanthanum oxide and/or other lanthanoid-containing oxides from a microelectronic device comprises contacting the lanthanum oxide or lanthanoid-containing oxide material with an etchant composition comprising, consisting of, or consisting essentially of a buffered halide system as the active ingredient. Preferably, the buffered halide system comprises, consists of or consists essentially of at least one [NR¹R²R³R⁴J⁺X^" salt as the active ingredient, wherein X = F, Cl, Br, and I, and R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained or branched CpC₆ alkyls (e.g., methyl, ethyl, propyl, butyl, pentyl, and hexyl) substituted or unsubstituted C₆-Ci₄ aryl (e.g., benzyl), and combinations thereof. More preferably, the buffered halide system comprises, consists of or consists essentially of at least one [NR¹R²R³R⁴J⁺Cl^" salt, [NR¹R²R³R⁴J⁺Br^" salt, [NR¹R²R³R⁴J⁺I^" salt, or combinations thereof as the active ingredient, wherein R¹, R², R³ and R⁴ are described above. Most preferably, the buffered halide system comprises, consists of or consists essentially of at least one [NR¹R²R³R⁴J⁺Cl^" salt as the active ingredient, wherein R¹, R², R³ and R⁴ are described above. Particularly preferred buffered chloride system salts include ammonium chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, and tetrabutylammonium chloride. In addition to the buffered halide system or as an alternative to the buffered halide system, a buffer such as potassium hydrogen phthalate in the presence of HCl may be considered. [0012] The pH of the buffered halide system is preferably in a range from about 3 to about 6, more preferably about 4 to about 6. The higher pH, the lower the etch rate of lanthanum oxide. In order to achieve the preferred pH, bases may be added for pH adjustment. For example, when the pH is required to be raised, a quaternary ammonium hydroxide such as tetramethylammonium hydroxide (TMAH) may be added. [0013] In a particularly preferred embodiment, the buffered halide systems and the etchant composition is substantially devoid of fluoride ions.

[0014] In still another embodiment, the etchant composition further includes lanthanum oxide or lanthanoid-containing oxides subsequent to initiation of etching. For example, the etchant composition may comprise, consist of or consist essentially of at least one buffered halide system as the active ingredient as defined above, and lanthanum oxide or lanthanoid- containing oxides. The lanthanum oxide or lanthanoid-containing oxides may be dissolved and/or suspended in the etchant composition. Preferably, the buffered halide system is substantially devoid of fluoride ions.

[0015] In yet another embodiment, the etchant composition further includes at least one passivating agent selected from the group consisting of sorbitol, ethylene glycol, propylene glycol, glycerol, and PEG (MW in a range from about 122 to 2000). The passivating agent preferably further reduces the lanthanum oxide and/or lanthanoid-containing oxide etch rates. [0016] Because the etchant compositions are aqueous-based and acidic, there is no damage to photoresist that may be present on the microelectronic device.

[0017] Preferably, the cumulative amount of at least one [NR¹R²R³R⁴J⁺X^' salt as the active ingredient is in a range from about 0.001 M to about 1 M, preferably about 0.005 M to about 0.5 M. One skilled in the art would know how to make an etchant composition having a certain molarity of [NR¹R²R³R⁴J⁺X^" salt dissolved therein, whether beginning with solid or liquid [NR¹R²R³R⁴J⁺X^" salt, a concentrated [NR¹R²R³R⁴J⁺X^" salt solution, or combining aqueous hydrogen halide acids with aqueous ammonia. Preferably, the water is deionized. [0018] In use, the etchant composition typically is contacted with the lanthanum oxide or lanthanoid-containing oxide for a time of from about 5 sec to about 10 min, preferably about 10 sec to about 180 sec, most preferably about 20 sec to about 90 sec, at temperature in a range of from about 5°C to about 60⁰C, preferably about room temperature. Such contacting times and temperatures are illustrative, and any other suitable time and temperature conditions may be employed that are efficacious to at least partially etch lanthanum oxide or lanthanoid- containing oxide. Preferably, the method removes excess lanthanum-oxide and/or other lanthanoid-containing oxides without damaging other materials present on the microelectronic device including, but not limited to, thermal oxide, polysilicon, high-k material (e.g., hafnium-containing materials), and combinations thereof.

[0019] In an etching application, an etching composition as described herein is contacted in any suitable manner to the microelectronic device having lanthanum oxide or lanthanoid- containing oxide thereon, e.g., by spraying an etchant composition on the surface of the device, by dipping (in a volume of an etchant composition) of the device including the lanthanum oxide or lanthanoid-containing oxide material, by contacting the device with another material, e.g., a pad, or fibrous sorbent applicator element, that has an etchant composition absorbed thereon, by contacting the device including the lanthanum oxide or lanthanoid-containing oxide with a spraying etchant, by contacting the device including the lanthanum oxide or lanthanoid-containing oxide with a recirculating etchant composition, or by any other suitable means, manner or technique, by which an etchant composition is brought into contact with the lanthanum oxide or lanthanoid-containing oxide. The contacting conditions include a period of time and conditions sufficient to etch the lanthanum oxide or lanthanoid-containing oxide.

[0020] Following the achievement of the desired removal action, the etchant composition may be readily removed from microelectronic device to which it has previously been applied using a rinse solution for time in a range from about 1 sec to about 60 sec, preferably about 10 sec to about 40 sec, wherein the rinse solution preferably comprises water, more preferably ultrapure water. Thereafter, the microelectronic device may be dried with nitrogen gas. [0021] The features and advantages of the invention are more fully shown by the illustrative examples discussed below.

Example 1

[0022] Six solutions were prepared as follows: Formulation A: 0.01 M NH₄Cl

Formulation B: 0.05 M NH₄Cl

Formulation C: 0.1 M NH₄Cl

Formulation D: 0.2 M NH₄Cl, adjusted to pH 6.08 with TMAH

Formulation E: 0. M NH₄Cl, adjusted to pH 8.6 with TMAH

Formulation F: 90 vol% 0.1 M NH₄Cl, 10.0 vol.% sorbitol

[0023] Blanketed lanthanum oxide coupons were dipped in a volume of formulations A-F, as well as pure water, for 30 sec, followed by withdrawal, and dip in rinsing water, and drying with nitrogen gas. The coupons were observed and the etch rates determined. The results are summarized in Table 1 below:

[0024] It can be seen that when the buffered chloride system has a pH between about 4 and about 6, there is excellent etch rate control with lanthanum oxide etch rates in a range from about 3 A min ¹ to about 50 A min^"1.

[0025] It is further noted that no damage to photoresist, hafnium oxide, titanium nitride or silicon oxide layers was observed when these materials were in the presence of formulations

A-F.

[0026] Although the invention has been variously disclosed herein with reference to illustrative embodiments and features, it will be appreciated that the embodiments and features described hereinabove are not intended to limit the invention, and that other variations, modifications and other embodiments will suggest themselves to those of ordinary skill in the art, based on the disclosure herein. The invention therefore is to be broadly construed, as encompassing all such variations, modifications and alternative embodiments within the spirit and scope of the claims hereafter set forth.

Claims

THE CLAIMSWhat is claimed is:

1. A method of etching lanthanum oxide or other lanthanoid-containing oxides from the surface of a microelectronic device having same thereon, said method comprises contacting the lanthanum oxide or lanthanoid-containing oxide material with an etchant composition under the appropriate contacting conditions, wherein the etchant composition comprises a buffered halide system as the active ingredient.

2. The method of claim 1, wherein the buffered halide system comprises at least one [NR¹R²R³R⁴J⁺X^" salt as the active ingredient, wherein X = F, Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained CpC₆ alkyls, branched CpC₆ alkyls, substituted C₆- Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

3 The method of claim 1 , wherein the buffered halide system consists of at least one

[NR¹R²R³R⁴J⁺X^' salt as the active ingredient, wherein X = F, Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained CpC₆ alkyls, branched CpC₆ alkyls, substituted C₆- Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

4. The method of claim 1, wherein the buffered halide system consists essentially of at least one [NR¹R²R³R⁴J⁺X^" salt as the active ingredient, wherein X = F, Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained CpC₆ alkyls, branched CpC₆ alkyls, substituted C₆-Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

5. The method of claim 1, wherein the buffered halide system comprises at least one

[NR¹R²R³R⁴J⁺X^' salt as the active ingredient, wherein X = Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained Ci-Ce alkyls, branched Ci-Cβ alkyls, substituted C₆- Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

6 The method of claim 1 , wherein the buffered halide system consists of at least one

[NR¹R²R³R⁴J⁺X^" salt as the active ingredient, wherein X = Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained CpC₆ alkyls, branched CpC₆ alkyls, substituted C₆- Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

7. The method of claim 1, wherein the buffered halide system consists essentially of at least one [NR¹R²R³R⁴J⁺X^" salt as the active ingredient, wherein X = Cl, Br or I, and wherein R¹, R², R³ and R⁴ may be the same as or different from one another and are selected from the group consisting of hydrogen, straight chained CpC₆ alkyls, branched CpC₆ alkyls, substituted C₆-Ci₄ aryl, unsubstituted C₆-Ci₄ aryl, and combinations thereof.

8. The method of any of claims 2-7, wherein the at least one [NR¹R²R³R⁴J⁺X^" salt is selected from the group consisting of ammonium chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, and combinations thereof.

9. The method of any of the preceding claims, wherein pH of the etchant composition is in a range from about 3 to about 6.

10. The method of claim 9, wherein the pH is adjusted using a base.

11. The method of any of claims 1, or 5-10, wherein the etchant composition is substantially devoid of fluoride ions.

12. The method of any of the preceding claims, wherein the amount of the at least one [NR¹R²R³R⁴J⁺X^" salt is in a range from about 0.001 M to about 1 M.

13. The method of any of the preceding claims, wherein the appropriate contacting conditions include time in a range from about 10 sec to about 180 sec.

14. The method of any of the preceding claims, wherein the appropriate contacting conditions include temperature in a range from about 5°C to about 60⁰C.

15. The method of any of the preceding claims, further comprising rinsing the etchant composition from the microelectronic device with a rinsing solution.

16. The method of claim 15, wherein the rinsing solution comprises water.

17. The method of claims 15 or 16, further comprising drying the microelectronic device.