TITANIUM ETCHANT COMPOSITION

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a metal etchant. More particularly, the present invention relates to a titanium etchant composition.

Description of Related Art

[0002] Titanium, one of the conductor materials, has been widely used in various fields, including integrated circuits, optoelectric communication, and even in the micro-electro-mechanical (MEM) field. For example, in a semiconductor fabricating process, titanium can be used as a wetting layer for an aluminum wire, so as to improve the step coverage ability of aluminum atoms. Titanium also can be used as a contact metal to reduce the contact resistance generated due to contact between the metal and silicon. Additionally, titanium can also be used as a barrier layer, an anti-reflective layer, and the like. As for the optoelectric field, gate electrodes, source electrodes, drain electrodes, scan lines, storage capacitor electrodes, signal lines, pixel lines, and the like may all utilize titanium or relevant alloy material.

[0003] In the process for fabricating a titanium film, a step of etching titanium is unavoidable, so it is especially important how to select a titanium etchant composition having a high etch rate to titanium, meanwhile without causing any corrosion to other films. [0004] For example, as for the flip chip bonding technique in the semiconductor packaging field, a conductor bump is directly connected to a chip, and a titanium film is required to be formed during the process of fabricating the bump. [0005] Referring to FIG 1, it is a schematic sectional diagram of a bump in a flip chip bonding technique. A chip 100 has an aluminum pad 110 formed thereon, and the aluminum pad 110 has a passivation layer 120 formed thereon, for protecting the chip 100. The protective layer 120 is generally made of silicon dioxide or silicon nitride. An opening of the aluminum pad 110 is covered by a under ball metallurgy layer 130 as

an interface of the aluminum pad 110 and the bump 140. The under ball metallurgy layer 130 is generally formed by an adhesion layer 130a, a barrier layer 130b, and a wetting layer 130c from bottom to top. The material of the adhesion layer 130a is, for example, titanium, the material of the barrier layer 130b is, for example, chromium, and the material of the wetting layer 130c is, for example, copper. When etching the adhesion layer 130a (the titanium film), most of the barrier layer 130b and the fusion layer 130c has already been etched. At this time, if the used titanium etchant causes corrosion to the materials, such as chromium, copper, aluminum, silicon dioxide, and silicon nitride, so that the patterns of other films will be unavoidably deformed, and each film lost its function, and even the electric property of the device is deteriorated.

SUMMARY OF THE INVENTION

[0006] Accordingly, the present invention is directed to a titanium etchant composition, applicable for reducing the corrosion on aluminum and a dielectric material by the etchant, so as to ensure the integrity of patterns for other films.

[0007] The present invention provides a titanium etchant composition, which at least includes hydrogen fluoride (HF), corrosion inhibitor, and water. The content of HF in the titanium etchant composition is, for example, 0.05 to 49 % by weight; and the content of the corrosion inhibitor is, for example, 0.1 to 99.9 % by weight. [0008] In the titanium etchant composition according to an embodiment of the present invention, the corrosion inhibitor is, for example, sodium silicate, azoles, organic acid, alcohols, ethers, or a mixture thereof.

[0009] In the titanium etchant composition according to an embodiment of the present invention, the azoles is, for example, benzotriazole (BTA), 2,3,5-triphenyl-2H-tetraazolium chloride (TTC), or a mixture thereof.

[0010] In the titanium etchant composition according to ^' an embodiment of the present invention, the organic acid is, for example, glycine, histidine (HS), glutamic acid, propylene glycol monomethyl acetate, amino tris (methylenephosphonic acid) (ATMP), l-hydroxyethylidene-l,l-diphosphonic acid (HEDP), or a mixture thereof. [0011] In the titanium etchant composition according to an embodiment of the present invention, the alcohols is, for example, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerol, butanol, pentanol, or a mixture

thereof.

[0012] In the titanium etchant composition according to an embodiment of the present invention, the ethers is, for example, butyl carbitol, diisopropyl ether, triisopropyl alcohol diether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, or a mixture thereof.

[0013] In the titanium etchant composition according to an embodiment of the present invention, the corrosion inhibitor is, for example, used to inhibit the corrosion of aluminum, chromium, copper, or a combination thereof. The corrosion inhibitor can also used to inhibit the corrosion of a dielectric material, and the dielectric material is, for example, silicon oxide or silicon nitride.

[0014] In the titanium etchant composition according to an embodiment of the present invention, the etch rate of the titanium etchant composition to aluminum, chromium, copper, or a combination thereof is, for example, less than 50 A/min; the etch rate of the titanium etchant composition to silicon oxide or silicon nitride is, for example, less than 10 A/min; and the etch rate of the titanium etchant composition to titanium is, for example, greater than 300 A/min. The etch selectivity of titanium to aluminum with the titanium etchant composition is greater than 6, and the etch selectivity of titanium to aluminum with the titanium etchant composition can also be greater than 15. [0015] In the titanium etchant composition according to an embodiment of the present invention, the titanium etchant composition is applicable for a flat panel display, an integrated circuit, a flip chip package, a printed circuit board, a color filter, a micro-electro-mechanical process, or another process comprising etching titanium. [0016] Since the corrosion inhibitor is utilized as an ingredient for the titanium ethcant composition in the present invention, the corrosion caused by the titanium etchant to aluminum and other dielectric materials can be effectively inhibited, so that the integrity of patterns of other films, except the titanium film, can be ensured, and the over etching and the deterioration of the electrical property of the device can be avoided. [0017] In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0019] FIG 1 is a schematic sectional diagram of a bump in a flip chip bonding technique.

DESCRIPTION OF EMBODIMENTS

[0020] The present invention provides a titanium etchant composition, which includes HF, corrosion inhibitor, and water. The content of HF is, for example, 0.05 to 49 % by weight, and the content of the corrosion inhibitor is 0.1 to 99.9 t% by weight. The corrosion inhibitor is, for example, sodium silicate, azoles, organic acid, alcohols, ethers, or a mixture thereof. Water can be ultra purified water or deionized water.

[0021] The azoles is, for example, benzotriazole (BTA) or 2,3,5-triphenyl-2H-tetraazolium chloride (TTC). In the titanium etchant of the present invention, an azole alone or a mixture of two of the above azoles can be used. [0022] The organic acid is, for example, glycine, histidine (HS), glutamic acid, propylene glycol monomethyl acetate, amino tris (methylenephosphonic acid) (ATMP), or l-hydroxyethylidene-l,l-diphosphonic acid (HEDP). In the titanium etchant of the present invention, an organic acid alone or a combination of the above organic acids can be used. [0023] The alcohols is, for example, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerol, butanol, or pentanol. The molecular weight of polyethylene glycol and polypropylene glycol is, for example, 200, 400, 600, 800, 1000, 2000, 4000, and 8000, and preferably, it is for example, 2000. In the titanium etchant of the present invention, an alcohol alone or a combination of the above alcohols can be used. [0024] The ethers is, for example, butyl carbitol, diisopropyl ether, triisopropyl alcohol diether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, or dipropylene glycol dimethyl ether. In the titanium etchant of the present invention,

an ether alone or a combination of the above ethers can be used. [0025] The corrosion inhibitor can be merely sodium silicate or one of the above organic compounds, or can be any combination of more than two compounds selected from the sodium silicate and the above organic compounds, which is added with HF and water to form a titanium etchant.

[0026] The corrosion inhibitor is, for example, used to inhibit the corrosion of the titanium etchant to aluminum, chromium, copper, or a combination thereof, and also used to inhibit the corrosion of the etchant to the dielectric material. The dielectric material is, for example, silicon oxide, silicon dioxide, silicon nitride, silicon oxynitride, borophospho silicate glass (BPSG), or phosphosilicate glass (PSG).

[0027] The etch rate of the titanium etchant of the present invention to aluminum, chromium, copper, or a combination thereof is, for example, less than 50 A/min; the etch rate of silicon oxide or silicon nitride is, for example, less than 10 A/min; and the etch rate of titanium is, for example, greater than 300 A/min. As known from the above that, the etch selectivity of titanium to aluminum with the titanium etchant composition is, for example, greater than 6. In preferred embodiments, the etch selectivity of titanium to aluminum with the titanium etchant composition can further be greater than 15. [0028] Since the corrosion inhibitor can be absorbed on the surface of the aluminum film, the titanium etchant of the present invention can inhibit the corrosion of the titanium etchant to aluminum and the dielectric material when etching titanium, so that the integrity of patterns of the aluminum film and other dielectric layers can be ensured. [0029] The experimental results obtained by etching the test sheet with the titanium etchant composition of the present invention and that obtained by only using HF as an etchant to perform the etching are illustrated below. [0030] [Experiment Procedures]

[0031] 1. Fabrication of a test sheet: the test sheet is fabricated by taking a chip generally used in a semiconductor process as a substrate, and forming a layer of thin film on the substrate. A plurality of sets of test sheets can be fabricated, each set includes 6 test sheets, and each test sheet has a different film formed thereon individually, which includes titanium film test sheet, aluminum film test sheet, chromium film test sheet, copper film test sheet, silicon dioxide film test sheet, and

silicon nitride film test sheet respectively.

[0032] 2. Formulation of titanium etchant of an experimental example and an etchant of a comparative example: the titanium etchant of the experimental example is formed by uniformly mixing 0.5 % by weight of HF, 10-30 % by weight of corrosion inhibitor, and 69.5-89.5 % by weight of water. The proportion of each ingredient for the titanium etchant in each experimental example is listed in Table 1. The etchant of the comparative example is formed by uniformly mixing 0.5 % by weight of HF and

99.5 % by weight of water.

[0033] 3. A photoresist layer is coated on the film layer of the test sheet, and then, a step of exposing and developing is performed, so as to pattern the photoresist layer on the test sheet, and thus forming a region to be etched on the film.

[0034] 4. An etching process is respectively performed on each set of test sheets with the formulated titanium etchant of the experimental example and the formulated etchant of the comparative example for a certain time period, at a temperature of 25°C. [0035] 5. The photoresist is removed, the height difference between the region to be etched and the region without being etched is measured, and the etch rate of each etchant to various films is calculated.

[0036] [Experimental Results]

[0037] 1. Comparative Example (0.5 % by weight of HF) [0038] Etch rate of titanium: 1260 (A/min)

[0039] Etch rate of aluminum: 1401 (A/min)

[0040] Etch selectivity of titanium to aluminum: 0.9

[0041 ] Etch rate of chromium: 0

[0042] Etch rate of copper: 0 [0043] Etch rate of silicon dioxide: 35 (A/min)

[0044] Etch rate of silicon nitride: 15 (A/min)

[0045] 2. Experimental example: referring to Table 1, the ingredients for the titanium etchant in each experimental example, the etch rate of each film, and the etch selectivity of titanium to aluminum are listed. [0046] Table 1

Ingredients for Titanium | Etch Rate (A/min) Etch

[0047] Obviously, it can be seen from Table 1 that, the etch rate of the titanium etchant added with the corrosion inhibitor to aluminum is considerably low. With such effect, the etch selectivity of titanium to aluminum in each experimental example can be greatly increased, which is even up to 20.6 (HF (0.5% by weight) + Glycine (20% by weight)). Therefore, it is known that, the corrosion inhibitor used in the present invention can indeed achieve the effect of inhibiting the corrosion of aluminum. [0048] In addition, HF used in the present invention will not etch chromium and

copper, and moreover, the corrosion on the dielectric material, such as silicon dioxide and silicon nitride, can be alleviated by adding the corrosion inhibitor. [0049] To sum up, the titanium etchant composition of the present invention can effectively increase the etch selectivity of the titanium to aluminum, chromium, copper, and dielectric materials, so that the technicians in this field can have a preferred control ability for the etching process on titanium, so as to improve the process window. The titanium etchant composition of the present invention can be applied in the various fields, such as a flat panel display (TFT LCD, LTPS, TN, STN, PDP, FED, SED, ELD, and VFD), an integrated circuit, a flip chip package, a printed circuit board, a color filter, a micro-electro-mechanical process, or another process comprising etching titanium. [0050] Furthermore, the titanium etchant composition of the present invention can greatly increase the etch selectivity of the titanium to the aluminum, chromium, copper, and dielectric materials, so as to ensure that each film containing aluminum, chromium, copper, and dielectric materials will not be etched by the etchant. In this way, the pattern of each film can be arranged according to the original design, and the integrity of the pattern is ensured, so that the device will have desirable electric properties, and thus further enhancing the reliability and stability of the product. [0051] Certainly, in the above experimental example, although 0.5 % by weight of HF and 10 to 30 % by weight of corrosion inhibitor is used to perform the test, this proportion is not used to limit the present invention, and the content of HF can be 0.05 to 49 % by weight, and the content of the corrosion inhibitor can be 0.1 to 99.9 % by weight. The etch selectivity of Ti/ Al obtained by utilizing a composition with different proportions of ingredients to perform the test may be higher than the data in the experimental example. [0052] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.