JP5304637B2 - Etching solution and etching method - Google Patents

Description

Field of Invention

  The present invention relates to an etchant useful for etching gold or palladium formed on a semiconductor or liquid crystal substrate. Moreover, this invention relates to the etching method performed using this etching liquid.

Background of the Invention

  Since noble metals such as gold or palladium are chemically stable, they are used in a wide variety of fields as materials for forming conductive contact portions and the like. In particular, gold is most often used as a material for forming a conductive contact portion and the like because it is chemically stable and an oxide film is not formed on the surface. Palladium has a lower oxidation potential and higher electrical resistance than gold, but is increasingly used as a seed wiring metal when the price is lower than gold.

  It is known that gold and palladium can be processed into a target shape by etching with aqua regia (nitric acid and hydrochloric acid) or iodine-based etching solution (see Patent Document 1).

  Among these etchants, aqua regia etchants are subject to equipment corrosion due to by-product nitrosyl gas (NOCl), and especially when sliding parts such as spin etching equipment corrode, there is a high risk of high-speed rotation. Use has not progressed since.

On the other hand, iodine-based etchants are used in recent years because of their high safety. An iodine-based etching solution is often an aqueous solution system because it is easy to dissolve and remove an iodide salt formed by oxidizing a metal (can be removed by washing with water and drying). However, the solubility of iodine in water is low. For this reason, when a water-containing iodine-based etching solution is used, a method is generally employed in which an iodide salt is used together with iodine and dissolved in the form of a double salt.
JP 49-123132 A

  In recent years, there has been a demand for an etchant that can efficiently etch a noble metal material present in a narrow gap as the bump width is reduced to improve the performance of the device.

Summary of the Invention

  The present invention provides an etching solution that is excellent in wettability with respect to a hydrophobic bare silicon wafer and that can efficiently etch gold or palladium existing in a narrow gap, and a method for etching gold or palladium using the etching solution The purpose is to provide.

  The present inventors diligently studied the above problems. As a result, it has been found that an etching solution containing a glycol ether compound, which is an oxygen-containing water-soluble organic solvent having surface activity, can efficiently etch even a noble metal material present in a narrow gap. Completed.

Etchant first aspect is a etchant gold or palladium, iodine, an iodide salt, containing water and glycol ether compound, the content of the glycol ether compound is Ru 16 to 80 wt% der It is characterized by that.

The etching liquid of the second aspect is characterized in that, in the etching liquid of the first aspect, the glycol ether compound is a glycol ether compound represented by the following general formula (1).
R ¹ —O— (R ² —O—) _n —H (1)
(1) In the formula, R ¹ represents an alkyl group having 4 to 20 carbon atoms, R ² represents an alkylene group having 2 to 4 carbon atoms, and n represents an integer of 2 to 40.

Etchant third aspect, in the first aspect or the etching liquid in the second state like, the contact angle against bare silicon wafer is equal to or less than 20 degrees.

The etching solution of the fourth aspect is characterized in that the iodine content in the etching liquid of any one of the first to third aspects is 0.5 to 5% by weight.

The etching solution according to the fifth aspect is characterized in that, in the etching liquid according to any one of the first to fourth aspects, the iodide salt content is 5 to 30% by weight in terms of potassium iodide. And

The etching solution according to the sixth aspect is characterized in that the molar concentration of iodide salt / iodine is 1.5 to 15.0 in the etching liquid according to any one of the first to fifth aspects.

The etching solution of the seventh aspect is characterized in that the glycol ether compound is diethylene glycol-n-butyl ether in any one of the etching liquids of the second to sixth aspects.

Etchant of the eighth aspect, in any one of the etching solution of the first aspect to seventh aspect, there is provided a etchant gold selectively etching the etching object gold and palladium coexist, glycol ether compounds The content of is 30% by weight or less.

Etchant of the ninth aspect, in any one of the etching solution of the first aspect to seventh aspect, there is provided a etchant palladium selectively etching the etching object gold and palladium coexist, glycol ether compounds The content of is not less than 50% by weight.

The etching method according to the tenth aspect is characterized in that gold or palladium is etched using the etching solution according to any one of the first to ninth aspects.

An etching method according to an eleventh aspect is characterized in that, in the etching method according to the tenth aspect, gold or palladium on the substrate is etched using a spin etching apparatus.

An etching method according to a twelfth aspect is characterized in that, in the etching method according to the tenth aspect or the eleventh aspect, a bump structure formed of gold or palladium on a semiconductor or liquid crystal substrate is etched.

The etching method of the thirteenth aspect is the same as the etching method of the twelfth aspect, in which the gold or palladium film between the gold bumps of the etching object in which the gold bumps are formed on the substrate via the gold or palladium film is etched. Features.

  According to the present invention, the wettability of a water-based etching solution containing iodine and iodide salt to a hydrophobic bare silicon wafer is greatly improved. For this reason, for example, in the production of various device devices such as semiconductors, liquid crystals, and LEDs, when forming wiring structures such as bumps on the substrate, a seed film made of gold or palladium in the gaps between the bumps is used. In the case of removing the etching, it is possible to eliminate the etching delay due to the difficulty of penetrating the etching solution, and to suppress the dissolution of the gold bump that progresses during the etching delay. Further, it is possible to suppress the roughening of the gold bump surface. As a result, it is possible to perform highly accurate and efficient etching, and high-quality products can be manufactured with high yield.

It is typical sectional drawing explaining the procedure of the formation method of the gold bump on the board | substrate with which the etching method of this invention is applied.

Detailed description

  Embodiments of the etching solution and etching method of the present invention will be described in detail below.

  The etching solution of the present invention contains iodine, iodide salt, water and glycol ether compound as essential components.

  The etching rate of the iodine / iodide salt aqueous solution etching solution depends on the concentration of iodine which is an oxidizing agent. The iodine concentration of the etching solution of the present invention is preferably 0.5% by weight or more, more preferably 0.8% by weight or more, preferably 5% by weight or less, more preferably 4% by weight or less. When the iodine concentration is not less than the above lower limit, it is easy to ensure a sufficient etching rate due to the oxidizing action. Moreover, when the iodine concentration is equal to or lower than the above upper limit, it is easy to suppress bump shape roughness.

  Iodine has low solubility in water. Therefore, in the present invention, iodine is used together with iodine to make iodine a double salt, which is dissolved in water.

The iodide salt used in the etching solution of the present invention is not particularly limited as long as it functions as an anion when iodine is dissolved in water. The iodide salt used in the etching solution of the present invention may be any as long as it can dissolve iodine in water. The valence of the iodide salt may be monovalent or divalent. Specific examples of the iodide salt include sodium iodide, ammonium iodide, and potassium iodide.
These iodide salts may be used individually by 1 type, and may use 2 or more types together.

  When iodine is dissolved in water as a double salt, the higher the iodide salt concentration, the higher the solubility of iodine. The iodide salt concentration of the etching solution of the present invention is preferably in the following range from the viewpoint of water solubility of iodine and reduction of the amount of residual iodine after etching. That is, the lower limit of the iodide salt concentration of the etching solution of the present invention is preferably 5% by weight, more preferably 6% by weight, particularly preferably 10% by weight, and the upper limit is preferably 30 in terms of potassium iodide. % By weight, more preferably 25% by weight, particularly preferably 18% by weight

  The lower limit of the molar ratio of iodide salt / iodine in the etching solution of the present invention is preferably 1.5, more preferably 3.0, and the upper limit is 15 from the viewpoint of etching rate and the like. Is preferably 0.0, more preferably 9.0.

  The total concentration of iodine and iodide salt in the etching solution of the present invention is preferably 6 to 35% by weight.

  The etching rate of the etching solution of the present invention may be affected by the presence of components other than iodine and iodide salts such as a glycol ether compound described later. In general, the etching rate tends to decrease as the concentration of components other than iodine and iodide salts in the etching solution increases. Therefore, the iodine and iodide salt concentrations of the etching solution need to be adjusted as appropriate so that the required etching rate can be obtained according to the types and concentrations of components other than iodine and iodide salts.

  The water used in the etching solution of the present invention is preferably highly pure, particularly when it is desired to obtain a highly clean surface such as fine wiring associated with semiconductor devices. Specifically, the water used in the etching solution of the present invention preferably has a specific resistance of 1 MΩ · cm or more, which is an index of the amount of conductive ions as impurities, and has a specific resistance exceeding 10 MΩ · cm or more. Pure water is particularly preferred.

  The etching solution of the present invention contains a glycol ether compound as an essential component.

In the present invention, the reason why an excellent etching solution that has not been achieved by the inclusion of a substance having a non-short molecular structure such as a glycol ether compound is not necessarily clear, but the cause is as follows. It seems like.
Conventionally, when a polar substance such as alcohol, glycol, glycerin, ether, ketone, ester, water-soluble carboxylic acid, or a compound having an oxygen atom having an unpaired electron is added to an iodine / iodide salt aqueous solution, the etching object It has been known that the wettability with respect to water is improved (see JP-A-49-014384, JP-A-58-016074, JP-A-63-176483 and JP-A-08-115656). .) That is, it has been considered that the wettability of the etching solution to the substrate is improved when a polar water-soluble organic solvent having an oxygen-containing compound such as alcohol or a nitrogen-containing compound such as N-methylpyrrolidone is contained. On the other hand, the glycol ether compound has both a hydrophobic group and a hydrophilic group in the molecule, and further has an ether group and an alcohol group that have a function of promoting distribution in dissociation of iodine. Accordingly, the glycol ether compound is resistant to iodine as an oxidizing agent and can be added in a large amount as a solvent to the etching solution. For this reason, the glycol ether compound in the etching solution of the present invention is unlikely to lose its function as a surfactant compared to the conventional etching solution in which only a small amount of normal surfactant is added. It is considered that the contact angle with bare silicon was lowered, and as a result, the noble metal material existing in the narrow gap could be efficiently etched.

The glycol ether compound used in the present invention is particularly preferably a glycol ether compound represented by the following general formula (1) from the viewpoint of solubility in water and safety.
R ¹ —O— (R ² —O—) _n —H (1)
(1) In the formula, R ¹ represents an alkyl group having 4 to 20 carbon atoms, R ² represents an alkylene group having 2 to 4 carbon atoms, and n represents an integer of 2 to 40.

In the glycol ether compound represented by the general formula (1), R ¹ is a hydrophobic group, and the alcohol part and the ether part of (R ² —O—) _n —H are hydrophilic groups. Here, if both ends are ether, the viscosity is low, but the solubility in water is low (the solubility in water when both ends are butyl ether is about 0.3% by weight), and there is a danger. Also gets higher.

In the general formula (1), ^{R 1} represents an alkyl group having 4 to 20 carbon atoms. The number of carbon atoms of the alkyl group represented by R ¹ is preferably large in terms of easily exhibiting the ability as a surfactant, but is preferably short from the viewpoint of solubility in water. From the viewpoint of easy availability, it is preferable that the alkyl group of R ¹ has 12 or less carbon atoms. The number of carbon atoms of the alkyl group represented by R ¹ is preferably 12 or less, more preferably 6 or less, from the viewpoint of solubility in water. Here, when the carbon number of the alkyl group of R ¹ is small, it is better to improve the wettability by increasing the concentration of the glycol ether compound in the etching solution because the surfactant ability of the glycol ether compound is low. Further, when R ¹ has a polymer structure, that is, a nonionic surfactant having a large number of carbon atoms in R ¹ , it is difficult to dissolve under acidic conditions. Therefore, when the etching solution is an acidic solution, the molecular weight of the hydrophilic portion and the hydrophobic portion can be adjusted to achieve a state excellent in both solubility and surface activity.

In the general formula (1), R ² represents an alkylene group having 2 to 4 carbon atoms. Among these, R ² is preferably an ethylene group or a propylene group, and more preferably an ethylene group, from the viewpoint of availability.

  In the glycol ether compound represented by the general formula (1), n is preferably 2 or more from the viewpoint of environmental problems. Further, n is preferably 4 or less from the viewpoint of wettability and viscosity.

Among the above glycol ether compounds, diethylene glycol-n represented by the following structural formula (2), wherein R ¹ is CH ₃ CH ₂ CH ₂ CH ₂ , R ² is CH ₂ CH ₂ and n is 2. -Butyl ether is preferred because it is readily available.

  These glycol ether compounds may be used alone or in combination of two or more.

  The concentration of the glycol ether compound in the etching solution of the present invention is preferably determined in consideration of the influence on the salting-out action of coexisting iodine and iodide salts, the etching rate of gold and / or palladium, and the like. The lower limit of the glycol ether compound concentration in the etching solution is preferably 16% by weight, more preferably 20% by weight, and the upper limit is preferably 80% by weight, and preferably 70% by weight. Further preferred is 65% by weight. When the concentration of the glycol ether compound is not less than the above lower limit, a uniform aqueous solution can be easily formed and phase separation hardly occurs even when the influence on the salting-out action of coexisting iodine and iodide salt is taken into consideration. It is preferable from the viewpoint of cost, etching rate and safety that the concentration of the glycol ether compound is not more than the above upper limit.

  In the etching solution of the present invention, as the concentration of the glycol ether compound increases, the etching rate of palladium becomes relatively higher than the etching rate of gold. Therefore, by adjusting the concentration of glycol ether compound in the etching solution according to the content and thickness of gold and palladium in the object to be etched, only one of gold and palladium is selectively used in the state where gold and palladium coexist. It becomes possible to perform etching. Specifically, for example, simultaneous etching of an alloy of gold and palladium, simultaneous etching of a multilayer film having a gold layer and a palladium layer can be performed. When only gold is etched in a state where gold and palladium coexist, the concentration of the glycol ether compound in the etching solution is preferably 30% by weight or less, and more preferably 25% by weight or less. In the case where only palladium is etched in the presence of gold and palladium, the concentration of the glycol ether compound in the etching solution is preferably 50% by weight or more, and more preferably 55% by weight or more.

  The etching solution of the present invention may contain components other than the iodine, iodide salt, water, and glycol ether compound as long as the effects of the present invention are not significantly impaired.

  The etching solution of the present invention can reduce the contact angle with respect to a hydrophobic substrate such as bare silicon and improve wettability, as shown in the examples described later.

This wettability can be evaluated by measuring the contact angle of the etching solution on the bare silicon wafer surface. Contact angle was measured according to JIS R3257 (1999) “Method for testing wettability of substrate glass surface” using a contact angle meter “CA-X150 type” manufactured by Kyowa Interface Science Co., Ltd. Is done.
Specifically, the contact angle is measured by the following procedure.
First, a 4-inch SUMCO silicon wafer (100 surfaces) is immersed in a 1% by weight hydrofluoric acid aqueous solution at room temperature (25 to 30 ° C.) for 1 minute, so that the silicon oxide film and impurities on the surface are immersed. Remove the metal to expose the bare hydrophobic surface. Next, under a dry nitrogen atmosphere, the silicon wafer is exposed to as little air as possible, and within 30 minutes from the bare hydrophobic surface exposure, one drop of the etching solution is placed on the silicon wafer. The contact angle is calculated by observing the state of the etching solution on the silicon wafer and performing image processing (three-point measurement method of a droplet image).

  The contact angle of the etching solution of the present invention thus measured is usually 20 degrees or less, preferably 10 degrees or less. The lower limit is usually 5 degrees or more. The measurement accuracy is usually ± 2 degrees.

  With the etching solution of the present invention, gold and palladium can be etched as shown in Examples described later.

  In general, since a metal becomes hard when it contains impurities, a high-purity metal is used for manufacturing a contact of a device such as a bump. Gold or palladium etched with the etching solution of the present invention preferably has a purity of 99.8% by weight or more. That is, in the case of gold, it is preferable that the purity of gold is 99.8% by weight or more, and in the case of palladium, the purity of palladium is preferably 99.8% by weight or more. Gold or palladium may be an alloy of gold and palladium. When the purity of gold or palladium is high, a desired etching process can be easily performed at a preferable etching rate.

  The method for etching gold or palladium using the etching solution of the present invention is not particularly limited as long as it can be etched by bringing the etching solution of the present invention into contact with a noble metal material to be etched. For example, the etching solution of the present invention may be used for etching by any method such as a dipping method (dip method), a spray method, or a spin method.

  There is no particular limitation on the apparatus used for the etching method of the present invention. However, in the etching method of the present invention, as described later, it is necessary to process the device substrate in a short liquid contact as in the case where gold or palladium on the substrate is etched using a “spin etching apparatus”. And is particularly effective when wettability is important.

  The etching conditions such as temperature and time during the etching process are not particularly limited as long as the target gold or palladium can be etched. About temperature, it determines suitably from a viewpoint of the film thickness of an etching target object, and an etching rate. In general, the etching rate increases as the temperature increases. However, when the temperature is high, if a volatile component is contained in the etching solution, this may evaporate and the composition of the etching solution may change. Therefore, the etching is usually performed at a room temperature of about 15 to 35 ° C. Done. In addition, when a highly volatile component is included in the etching solution, in order to suppress fluctuations in the liquid composition due to evaporation, a process such as adjusting the concentration by adding additional evaporation to the etching solution may be performed.

  The etching method of the present invention is particularly effective when etching a gold bump structure formed on a semiconductor or liquid crystal substrate. In particular, when manufacturing various device devices such as semiconductors, liquid crystals, and LEDs, for example, wiring structures such as bumps are formed on various substrates such as silicon substrates, glass substrates, III-V group substrates, and ceramic substrates. It is preferably used in some cases.

A specific procedure of the etching method in this case will be described with reference to FIG.
First, a base layer made of Ti, TiW or the like serving as an adhesive layer is formed on the substrate 1 (FIGS. 1A and 1B). A seed film (seed wiring) 3 of gold and / or palladium is formed on the base layer 2 (FIG. 1C). A photoresist layer 4 is patterned on the seed film 3 so as to partially cover the seed film 3 (FIG. 1D), and then the surface of the seed film 3 on which the photoresist layer 4 is not formed. After the gold bump wiring 5 is formed on the protruding portion by plating or the like (FIG. 1 (e)), the photoresist layer 4 is removed (FIG. 1 (f)). Thereafter, the gold and / or palladium seed wiring 3 in the exposed portion of the seed film 3 where the gold bump wiring 5 is not formed is removed by etching (FIG. 1G). Further, the underlying layer 2 at the exposed portion of the underlying layer 2 where the gold bump wiring 5 is not formed is removed (FIG. 1 (h)).

  In forming the gold bump on the substrate, the etching method of the present invention removes the exposed portion of the seed wiring 3 made of gold and / or palladium partially formed with the gold bump wiring 5 by etching. (Etching from the state of FIG. 1 (f) to the state of FIG. 1 (g)).

Since the etching solution of the present invention is excellent in wettability with respect to these objects to be etched, it is considered that the etching solution easily enters a narrow gap between narrow bumps.
In general, in an iodine-based etching solution, a dissolved gold and / or palladium salt suppresses new etching of gold and / or palladium. For example, when gold on a silicon substrate is etched only by longitudinal swing, a difference in etching rate tends to occur between the upper and lower portions of the substrate. This tendency becomes more remarkable as the substrate becomes larger, and it becomes difficult to maintain in-plane uniformity. Here, when etching is performed using a spin etching apparatus, the retention time of the etching solution is short, so that the etching solution is excellent in wettability, and this is effective for eliminating the deposited gold and / or palladium salt. It is easy to etch uniformly in the surface. For this reason, the etching solution of the present invention works very effectively especially when a spin etching apparatus is employed. In addition, when the wettability is improved, differences in the etching rate in the vertical, horizontal, and height directions of the noble metal bump column are less likely to occur, the surface roughness is likely to be reduced, and the bump shape is easily maintained. Such an effect is manifested only when the wettability of the etching solution is extremely high.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to a following example, unless the summary is exceeded.

<Manufacture of gold deposition substrate (1) and gold bump substrate (1)>
A glass substrate (“# 1737 (thickness 0.7 mm / length 50 mm / width 50 mm)” manufactured by Corning Japan Co., Ltd.) was washed with “Semico Clean 56” manufactured by Furuuchi Chemical Co., Ltd. (FIG. 1A). Using an ULVAC high-frequency sputtering apparatus “SH-350”, sputtering was performed at a sputtering output of 400 W for 10 minutes to form a 290 nm-thick titanium underlayer on the glass substrate (FIG. 1B). Then, sputtering was performed at a sputtering output of 400 W for 10 minutes, and a gold film having a film thickness of 160 nm was formed as a seed wiring film on the titanium base film (the substrate in this state is hereinafter referred to as “gold film forming substrate”). (FIG. 1 (c)) Next, a photoresist “PMER P-LA900PM” manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied to the gold film formation substrate. The film was applied to a thickness of 20 μm and post-baked for 6 minutes at 110 ° C. After that, exposure was performed for 2 minutes with a proximity mask aligner “PLA-501F” manufactured by Canon Inc. Development was performed with a developer “PMER P-7G” manufactured by Kogyo Co., Ltd. for 4 minutes to obtain a patterning substrate (having holes in the bump portions) (FIG. 1D).

On the patterned substrate, using a bath solution “K-740 Pure Gold” manufactured by Kojima Chemical Co., Ltd. and a microcell model I (300 cm ³ ) manufactured by Yamamoto Kakin Tester Co., Ltd. Gold plating was performed. Gold plating is carried out using a constant current device (“Sourcemeter 2400” manufactured by Keithley Instruments Co., Ltd.) while holding the plating solution at 60 ° C. while agitating with an L-shaped metal fitting attached to an MCR18 cathode rocker. Gold bumps having a width of 10 μm and a height of 10 μm (a gap between the bumps of 10 μm) were formed (FIG. 1E). Thereafter, the resist film is removed with acetone, and a substrate (gold bump pillar / gold seed film (thickness 160 nm) / titanium underlayer (on which gold bump columns (line / space = 10/10) are formed) is formed on the surface. Film thickness 290 nm) / glass substrate) was produced (FIG. 1 (f)). This substrate was cut into 2 cm × 2 cm to prepare “gold bump substrate (1)” for etching test.

  Separately, a gold film formation substrate (gold seed film (film thickness: 160 nm) / titanium underlayer film (film thickness: 290 nm) / glass substrate) manufactured in the same manner as described above was cut into 2 cm × 2 cm, and “gold Deposition substrate (1) ”was produced.

<Production of Palladium Film Formation Substrate (2) and Gold Bump Substrate (2)>
On a glass substrate similar to that used for the production of the gold bump substrate (1) described above, a plate having a 200 nm-thick titanium underlayer formed thereon and a 200 nm-thick palladium film formed thereon, Purchased from Furuya Metal Co., Ltd. (the substrate in this state is hereinafter referred to as “palladium film-forming substrate”). A photoresist “PMER P-LA900PM” manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied to the palladium film-forming substrate so as to have a resist film thickness of 20 μm, and post-baked at 110 ° C. for 6 minutes. Thereafter, exposure is performed for 3 minutes with a proximity mask aligner “PLA-501F” manufactured by Canon Inc., and development is performed for 4 minutes with a developer “PMER P-7G” manufactured by Tokyo Ohka Kogyo Co., Ltd. A substrate with a hole in the part was obtained (FIG. 1 (d)).

  On this patterned substrate, gold plating was performed in the same manner as in the above-mentioned “manufacture of gold bump substrate (1)”, and then the resist film was removed with acetone to form a row of gold bumps (line / space = 10/10). ) Was prepared (gold bump pillar / palladium seed film (film thickness 200 nm) / titanium underlayer film (film thickness 200 nm) / glass substrate)) (FIG. 1F). This substrate was cut into 2 cm × 2 cm to prepare “gold bump substrate (2)” for an etching test.

  Separately, a palladium film formation substrate (palladium seed film (film thickness 200 nm) / titanium underlayer film (film thickness 200 nm) / glass substrate) is cut into 2 cm × 2 cm, and “palladium film formation substrate (2)” for etching test Was made.

<Physical property evaluation>
The following evaluation was performed about the wettability of the etching liquid shown in the below-mentioned Example and a comparative example, the etching rate, and the surface roughness of the bump before and behind etching.
1) Wetting property of etching solution The contact angle when one drop of each etching solution was dropped on bare silicon was measured by the above-mentioned apparatus and conditions, and the wetting property was evaluated (the smaller the contact angle, the better the wetting property). ).
2) Etching speed of gold or palladium seed film portion in the gap between bumps Using a laser microscope (Red Semiconductor Laser Microscope “VK-8500” manufactured by Keyence Corporation), presence or absence of gold or palladium seed film residue on the substrate after etching Was observed visually, and the etching rate of the gold or palladium seed film in the space between the bumps was calculated from the time required for the gold or palladium seed film in the bump gap to be completely removed.
3) Etching speed of gold bump structure The vertical, horizontal and height of 10 bumps on the substrate before etching were measured with the laser microscope, and the average value was calculated. Next, the shape of 10 bumps after the etching treatment was measured, the average value of the amount of decrease in the vertical, horizontal, and height directions was calculated, and the average etching rate of the gold bumps was calculated.
4) Bump surface roughness (Ra) before / after etching
The upper surface of 10 bumps was measured with the laser microscope, and the average value of the surface roughness (Ra) was calculated by performing numerical calculation by longitudinal image processing. The “gold bump substrate (1)” before etching had a golden metallic luster, and the average roughness (Ra) of the bump surface was 60 nm. When becomes larger, irregular reflection occurs on the surface of the substrate, so that the substrate emits a dull luster. In addition, the average roughness (Ra) of the bump surface of the “gold bump substrate (2)” before etching was 60 nm.

<Example 1>
As an etching solution for etching the gold film in the seed part of the bump gold gap, an etching solution containing 3% by weight of iodine, 12% by weight of potassium iodide, 20% by weight of diethylene glycol-n-butyl ether and 65% by weight of ultrapure water was prepared. . The contact angle measured by dropping this etching solution on the bare silicon wafer was 9.0 degrees.
A glass beaker containing 200 cm ^{3 of an} etching solution was placed in a constant temperature water bath at 30 ° C. With this etching solution, “gold bump substrate (1)” (2 cm × 2 cm: gold bump pillar / gold seed film (film thickness 160 nm) / titanium underlayer film (thickness 290 nm) / glass substrate) for etching test is hand-dip dip After performing the etching process by the method, it was washed and dried.

The etching rate of the gold seed film in the bump gap was 137 nm / min. The bump etching rate was 79.4 nm / min in the vertical (length) direction, 85.6 nm / min in the horizontal (width) direction, and 128 nm / min in the same height direction. That is, the ratio of the bump etching rate to the etching rate of the gold seed film in the bump gap was 0.58 to 0.93 times, and the bump shape was sufficiently maintained after the etching. In particular, the etching rate ratio for “the height direction of the gold bump”, which is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc., was 0.93 times as good.
The substrate after etching exhibited a gold gloss color visually. Further, the surface roughness (Ra) of the bump was 110 nm and the surface roughness was small.

<Comparative Example 1>
Instead of the etching solution of Example 1, an etching solution containing 3% by weight of iodine, 12% by weight of potassium iodide, 20% by weight of n-methyl-2-pyrrolidone and 65% by weight of ultrapure water was used. Etching was performed in the same manner as in Example 1. The contact angle measured by dropping this etching solution on the bare silicon wafer was 33.0 degrees. This value is substantially equivalent to the contact angle of 32.6 degrees described in Japanese Patent Application Laid-Open No. 2004-211142.

The etching rate of the gold seed film in the bump gap was as high as 480 nm / min. However, the etching rate of the bumps is 518 nm / min in the vertical (length) direction, 289 nm / min in the horizontal (width) direction, and 479 nm / min in the same height direction, particularly in the vertical (length) direction. The speed was faster than the etching speed of the gold seed film in the bump gap, and the height direction was equally fast. That is, the ratio of the bump etching rate to the etching rate of the gold seed film in the bump gap was 0.60 to 1.08. In particular, it is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc. The “gold bump height direction” is 1.00 times that of the gold seed film. It was.
Further, the surface roughness (Ra) of the bumps of the substrate after etching was 170 nm, and the surface was rough.

<Comparative example 2>
Etching was performed in the same manner as in Comparative Example 1 except that 1-propanol was used instead of n-methyl-2-pyrrolidone in the etching solution of Comparative Example 1. The contact angle measured by dropping this etching solution onto the bare silicon wafer was 30 degrees.
The etching rate of the gold seed film in the bump gap was as high as 240 nm / min. However, the etching rate of the bumps was as fast as 307 nm / min in the vertical (length) direction, 211 nm / min in the horizontal (width) direction, and 259 nm / min in the same height direction. That is, the ratio of the bump etching rate to the etching rate of the gold seed film in the bump gap was 0.88 to 1.28 times. In particular, it is important to suppress the etching speed because it is involved in the connection between the panel and the driver, etc. The “gold bump height direction” was 1.08 times higher than the gold seed film. .
Further, the substrate after etching exhibited a dull golden fading gloss, and the surface roughness (Ra) of the bumps was 190 nm, which was rough.

<Comparative Example 3>
Etching was performed in the same manner as in Comparative Example 1 except that diethylene glycol was used instead of n-methyl-2-pyrrolidone in the etching solution of Comparative Example 1. The contact angle measured by dropping this etching solution on the bare silicon wafer was 40 degrees.
The etching rate of the gold seed film in the bump gap was as fast as 320 nm / min. However, the etching rate of the bumps was 747 nm / min in the vertical (length) direction, 604 nm / min in the horizontal (width) direction, and 724 nm / min in the same height direction. That is, the ratio of the etching rate of the bump to the etching rate of the gold seed film in the bump gap was 1.89 to 2.33 times. In particular, it is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc. The “gold bump height direction” was 2.26 times higher than the gold seed film. .
Further, the substrate after the etching exhibited a dull golden fading gloss, and the surface roughness (Ra) of the bump was 200 nm, which was rough.

  The results of Example 1 and Comparative Examples 1 to 3 are summarized in Table 1. From Table 1, it is clear that excellent etching characteristics can be obtained by the etching solution of the present invention.

<Reference Example 1>
An attempt was made to prepare an etching solution of 3% by weight of iodine, 12% by weight of potassium iodide, 15% by weight of diethylene glycol-n-butyl ether, and 70% by weight of ultrapure water, but it was separated into two phases, an aqueous layer and an organic solvent layer. I have. When separated into two phases, iodine that determines the etching rate is distributed and concentrated on the organic layer side, and the etching target comes into contact with the concentrated iodine solution, so it is difficult to control the etching selectivity between the seed noble metal material and the bump material. It is.

<Example 2>
As an etching solution for etching the palladium film in the seed part of the bump gold gap, an etching solution containing 3% by weight of iodine, 12% by weight of potassium iodide, 60% by weight of diethylene glycol-n-butyl ether and 25% by weight of ultrapure water was prepared. . The contact angle measured by dropping this etching solution onto the bare silicon wafer was 4 degrees.
A glass beaker containing 200 cm ^{3 of an} etching solution was placed in a constant temperature water bath at 35 ° C. With this etching solution, “gold bump substrate (2)” (2 cm × 2 cm: gold bump pillar / palladium seed film (thickness: 200 nm) / titanium underlayer (thickness: 200 nm) / glass substrate) for etching test is hand-dip dip After performing the etching process by the method, it was washed and dried.

The etching rate of the palladium seed film in the bump gap was 200 nm / min. Further, the etching rate of the bumps was 62 nm / min in the vertical (length) direction, 46 nm / min in the horizontal (width) direction, and 32 nm / min in the same height direction. That is, the etching rate ratio of the gold bump to the etching rate of the palladium seed film in the gap between the bumps was 0.16 to 0.31 times, and the bump shape was sufficiently maintained after the etching. In particular, the etching rate ratio for “the height direction of the gold bumps”, which is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc., was very good at 0.16 times.
Further, the surface roughness (Ra) of the bump after etching was 70 nm, and the surface roughness was very small.

<Comparative example 4>
Instead of the etching solution of Example 2, an etching solution containing 3% by weight of iodine, 12% by weight of potassium iodide, 60% by weight of n-methyl-2-pyrrolidone and 25% by weight of ultrapure water was used. Etching was performed as in 2. The contact angle measured by dropping this etching solution onto the bare silicon wafer was 19.5 degrees.

The etching rate of the palladium seed film in the gap between the bumps was 218 nm / min, which was almost the same as that in Example 2 using diethylene glycol-n-butyl ether, but the etching rate of the bump was in the longitudinal (length) direction. Was 53 nm / min, the horizontal (width) direction was 62 nm / min, and the height direction was 174 nm / min. That is, the ratio of the bump etching rate to the etching rate of the palladium seed film in the gold bump gap was 0.24 to 0.80. In particular, the “gold bump height direction”, which is important to suppress the etching rate because it is involved in the connection between the panel and the driver, is as large as 0.80 times, and the surface roughness of the bump after etching is large. The degree (Ra) was 100 nm and the surface was rough.
From these results, it is clear that in Comparative Example 4, the etching of the gold bump accompanying the etching of the palladium seed film proceeds excessively as compared with Example 2.

<Comparative Example 5>
Etching was performed in the same manner as in Comparative Example 4 except that 1-propanol was used instead of n-methyl-2-pyrrolidone in the etching solution of Comparative Example 4. The contact angle measured by dropping this etching solution onto the bare silicon wafer was 8.9 degrees.
The etching rate of the palladium seed film in the bump gap was as fast as 667 nm / min. The etching rate of the gold bumps was 356 nm / min in the longitudinal (length) direction, 245 nm / min in the horizontal (width) direction, and 473 nm / min in the height direction. That is, the ratio of the bump etching rate to the etching rate of the palladium seed film in the gap between the bumps was 0.37 to 0.71 times. In particular, the “gold bump height direction”, which is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc. is 0.71 times larger, and the bump surface roughness after etching is also large. The degree (Ra) was 80 nm and the surface was rough.
From these results, it is clear that in Comparative Example 5, the etching of the gold bump accompanying the etching of the palladium seed film proceeds excessively as compared with Example 2.

<Comparative Example 6>
Etching was performed in the same manner as in Comparative Example 4 except that diethylene glycol was used instead of n-methyl-2-pyrrolidone in the etching solution of Comparative Example 4. The contact angle measured by dropping this etching solution on the bare silicon wafer was 38.5 degrees.
The etching rate of the palladium seed film in the bump gap was as high as 240 nm / min. However, the etching rate of the gold bumps was 504 nm / min in the vertical (length) direction, 346 nm / min in the horizontal (width) direction, and 551 nm / min in the same height direction. That is, the ratio of the bump etching rate to the etching rate of the palladium seed film in the gap between the bumps was 1.44 to 2.30 times. In particular, the “gold bump height direction”, which is important to suppress the etching rate because it is involved in the connection between the panel and the driver, etc., is 2.30 times larger, and the bump surface roughness after etching is also large. The degree (Ra) was 140 nm and the surface was rough.
From these results, it is clear that in Comparative Example 6, the etching of the gold bump accompanying the etching of the palladium seed film proceeds excessively as compared with Example 2.

  The results of Example 2 and Comparative Examples 4 to 6 are summarized in Table 2. From Table 2, it is clear that the etching solution of the present invention provides excellent etching characteristics capable of maintaining the height of the gold bump.

<Example 3>
A glass beaker containing 200 cm ^{3 of} an etching solution having the same composition as that used in Example 1 was placed in a constant temperature water bath at 35 ° C. With this etching solution, “gold deposition substrate (1)” (2 cm × 2 cm: gold seed film (thickness 160 nm) / titanium underlayer (thickness 290 nm) / glass substrate) and “palladium deposition substrate (2) ”(2 cm × 2 cm: Palladium seed film (film thickness 200 nm) / titanium underlayer film (film thickness 200 nm) / glass substrate) were each etched by a hand shake dipping method, then washed with water and dried. .
The etching rate was 253 nm / min for the gold seed film and 78 nm / min for the palladium seed film. That is, the ratio of the etching rate of the palladium seed film to the etching rate of the gold seed film was 0.31.

<Example 4>
An etching solution containing 3% by weight of iodine, 12% by weight of potassium iodide, 40% by weight of diethylene glycol-n-butyl ether and 45% by weight of ultrapure water was prepared. The contact angle measured by dropping this etching solution onto the bare silicon wafer was 13 degrees.
Etching was similarly performed using this etching solution instead of the etching solution of Example 3.
The etching rate was 113 nm / min for the gold seed film and 131 nm / min for the palladium seed film. That is, the ratio of the palladium seed film etching rate to the gold seed film etching rate was 1.16.

<Example 5>
Instead of the etching solution of Example 3, an etching solution having the same composition as that used in Example 2 (iodine 3% by weight, potassium iodide 12% by weight, diethylene glycol-n-butyl ether 60% by weight and ultrapure water 25% by weight) %) Was used for the same etching.
The etching rate was 50 nm / min for the gold seed film and 200 nm / min for the palladium seed film. That is, the ratio of the palladium seed film etching rate to the gold seed film etching rate was 4.0.

  The results of Examples 3 to 5 are summarized in Table 3.

<Comparative Examples 7-9>
Etching was performed in the same manner as in Examples 3 to 5 except that n-methyl-2-pyrrolidone was used instead of diethylene glycol-n-butyl ether in the etching solutions of Examples 3 to 5. The results are shown in Table 4.

<Comparative Examples 10-12>
Etching was performed in the same manner as in Examples 3 to 5 except that 1-propanol was used instead of diethylene glycol-n-butyl ether in the etching solutions of Examples 3 to 5. The results are shown in Table 5.

<Comparative Examples 13-15>
Etching was performed in the same manner as in Examples 3 to 5 except that diethylene glycol was used instead of diethylene glycol-n-butyl ether in the etching solutions of Examples 3 to 5. The results are shown in Table 6.

  From Tables 3-6, since the palladium / gold etching rate ratio differs greatly with respect to the density | concentration of the diethylene glycol-n-butyl ether in etching liquid, the etching liquid of this invention uses diethylene glycol using the etching liquid of this invention. It has been found that selective etching of gold and palladium is possible by adjusting the concentration of n-butyl ether.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on March 12, 2007 (Japanese Patent Application No. 2007-62066) and a Japanese patent application filed on September 19, 2007 (Japanese Patent Application No. 2007-242532). Which is incorporated by reference in its entirety.

Claims (13)

A etching liquid gold or palladium, iodine, an iodide salt, containing water and glycol ether compound, the etching solution content of glycol ether compound is characterized by 16 to 80 wt% der Rukoto. The etching liquid according to claim 1, wherein the glycol ether compound is a glycol ether compound represented by the following general formula (1).
R ¹ —O— (R ² —O—) _n —H (1)
(1) In the formula, R ¹ represents an alkyl group having 4 to 20 carbon atoms, R ² represents an alkylene group having 2 to 4 carbon atoms, and n represents an integer of 2 to 40. The etching solution according to claim 1 or 2 , wherein a contact angle with respect to the bare silicon wafer is 20 degrees or less. The etching solution according to any one of claims 1 to 3 , wherein the iodine content is 0.5 to 5% by weight. In the etching solution according to any one of claims 1 to 4, the etching liquid content of iodide salts, characterized in that 5 to 30% by weight content in terms of potassium iodide. The etching solution according to any one of claims 1 to 5 , wherein the molar concentration of iodide salt / iodine is 1.5 to 15.0. The etching liquid according to any one of claims 2 to 6 , wherein the glycol ether compound is diethylene glycol-n-butyl ether. The etching solution according to any one of claims 1 to 7 , wherein the etching solution selectively etches gold as an etching target in which gold and palladium coexist, and the content of the glycol ether compound is 30% by weight. Etching liquid characterized by being less than or equal to%. In the etching solution according to any one of claims 1 to 7, a etchant that selectively etches the palladium etching object gold and palladium coexist, the content of the glycol ether compound is 50 weight Etching solution characterized by being at least%. 10. An etching method comprising etching gold or palladium using the etching solution according to any one of claims 1 to 9 . The etching method according to claim 10 , wherein gold or palladium on the substrate is etched using a spin etching apparatus. In the etching method according to claim 10 or 11, etching method characterized by etching a bump structure formed by gold or palladium on a substrate for semiconductor or liquid crystal. 13. The etching method according to claim 12 , wherein the gold or palladium film between the gold bumps is etched on the object to be etched in which the gold bump is formed on the substrate via the gold or palladium film. Method.

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