JP2009026786A - Cleaning liquid and cleaning method for semiconductor device having gold electrode or gold wiring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning liquid which removes iodine and an iodine compound that remain in a semiconductor device, when etching by using an iodine based etching liquid to form a gold electrode or gold wiring in the semiconductor device, and which will not give secondary damages to the semiconductor device, and to provide a cleaning method that uses the cleaning liquid, and the high-reliability semiconductor device cleaned by this cleaning method. <P>SOLUTION: This cleaning liquid is for cleaning iodine and the iodine compound that remain in the semiconductor device, having the gold electrode or the gold wiring formed by the iodine based etching liquid, and the cleaning liquid is an aqueous solution containing thiosulfate; and this cleaning method uses the cleaning liquid, and the semiconductor device is cleaned by this cleaning method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cleaning liquid and a cleaning method for a semiconductor device having a gold electrode or a gold wiring. Specifically, the present invention relates to a cleaning solution and a cleaning method for removing iodine and iodine compounds remaining in a semiconductor device when wet etching of a gold thin film, a gold electrode, or a gold wiring on a semiconductor device is performed with an iodine-based etching solution.

  Gold and gold alloys are widely used as materials for forming electrodes and wirings of semiconductor devices and liquid crystal display elements. As a technique for forming fine electrodes and wiring patterns made of gold or a gold alloy, a wet etching method has become widespread. As an etchant used for gold or a gold alloy, an iodine-based etchant is known (see, for example, Patent Documents 1 and 2). Iodine-based etchants are advantageous in that they easily react with gold and gold alloys, have a high etching rate, and are easy to handle.

  However, when an iodine-based etching solution is used, iodine and iodine compounds may remain in the semiconductor device, and the residual iodine and iodine compounds may induce gold migration. For this reason, after the etching is completed, the semiconductor device must be cleaned to sufficiently remove excess iodine-based etching solution so that iodine and iodine compounds do not remain in the semiconductor device. Usually, ultrapure water is used for cleaning excess iodine-based etching solution, but it is not always sufficient, and a chemical suitable for higher-level cleaning is required.

  However, as a matter of course, chemicals for cleaning iodine and iodine compounds remaining in the semiconductor device should not cause secondary damage such as corrosion to the semiconductor device. When damage such as corrosion occurs, extreme unevenness occurs on the vertical surface of the fine bump electrode that extends in a direction substantially perpendicular to the silicon substrate surface. For example, a groove between the bump electrodes is filled with a thermosetting resin. In some cases, voids may be generated and the reliability of the semiconductor device may be impaired.

Japanese Patent Publication No.51-20976 JP 2003-229420 A

  The present invention substantially completely removes iodine and iodine compounds remaining in a semiconductor device when etching with an iodine-based etchant to form a gold electrode or a gold wiring in the semiconductor device, It is an object of the present invention to provide a cleaning solution that does not cause any damage, a cleaning method using the cleaning solution, and a highly reliable semiconductor device cleaned by the cleaning method.

  The present inventors have intensively studied. As a result, a cleaning liquid for cleaning iodine and iodine compounds remaining in a semiconductor device having a gold electrode or a gold wiring formed with an iodine-based etching liquid, the cleaning liquid being an aqueous solution containing a thiosulfate, Knowing that the above-mentioned problems can be solved by a cleaning method using the same and a semiconductor device cleaned by the cleaning method, the present invention has been completed based on the knowledge.

The present invention is constituted by the following.
(1) A cleaning solution for cleaning iodine and iodine compounds remaining in a semiconductor device having a gold electrode or a gold wiring formed with an iodine-based etching solution, and the cleaning solution is an aqueous solution containing thiosulfate A characteristic cleaning solution.
(2) The cleaning liquid according to (1) above, wherein the cleaning liquid contains 0.5 to 10% by weight of thiosulfate.
(3) The cleaning liquid according to (1) or (2) above, wherein the thiosulfate is sodium thiosulfate.
(4) Washing iodine and iodine compounds remaining by immersing a semiconductor device having a gold electrode or gold wiring formed with an iodine-based etching solution in the cleaning solution according to any one of (1) to (3) above A cleaning method comprising removing and then cleaning the immersed semiconductor device with ultrapure water.
(5) A semiconductor device having a gold electrode or a gold wiring formed by an iodine-based etchant that has been cleaned by the cleaning method described in (4) above.
(6) The amount of iodine and iodine compound remaining in the semiconductor device per silicon wafer substrate with a diameter of 200 mm (8 inches) having a semiconductor device having a gold electrode or gold wiring formed on the entire upper surface of the silicon wafer substrate, The semiconductor device according to (5), wherein the amount is 1 μg or less in terms of iodine.

  According to the present invention, iodine and iodine compounds remaining in a semiconductor device having a gold electrode or a gold wiring formed by an iodine-based etching solution can be reduced and removed almost completely by the cleaning solution of the present invention. A highly reliable semiconductor device can be obtained without fear of occurrence.

  For example, a semiconductor device such as an IC chip usually uses a silicon wafer as a substrate, a connection electrode base metal layer formed on the silicon substrate, and a bump electrode made of gold or a gold alloy formed on the base metal layer Consists of. Here, the base metal layer includes a base metal base layer made of Ti / W, Ti / N, Ti / Pt or Ti and a base metal surface layer made of gold or a gold alloy. The base metal surface layer is formed to improve the adhesion between the base metal base layer and the bump electrode.

  First, a base metal base layer having a thickness of 0.05 to 1 μm is formed on the entire surface of the silicon substrate by sputtering. Further, a base metal surface layer made of gold or a gold alloy having a thickness of 0.05 to 1 μm is formed on the base metal base layer. A plating resist layer is formed by a photolithography method on the surface of the base metal surface layer other than the region where the bump electrode is to be formed. Next, a bump electrode is formed by depositing gold or a gold alloy having a predetermined thickness on the surface of the base metal surface layer where the bump electrode is to be formed by plating. The bump electrode is a protruding electrode protruding substantially perpendicular to the silicon substrate surface.

  Next, the plating resist layer is peeled and removed by a method such as dipping in a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) heated to 40 to 100 ° C. for 5 to 30 minutes, for example. As a result, the underlying metal surface layer (gold or gold alloy) covered with the plating resist layer is exposed. This base metal surface layer is removed by etching with an iodine-based etchant and washed with ultrapure water, and then the base metal base layer is also etched (for example, etching with hydrogen peroxide in the case of a Ti / W layer). Remove and wash with ultrapure water. As a result, a semiconductor device is formed which has fine bump electrodes extending in a direction substantially perpendicular to the silicon substrate surface, and the base metal base layer and the base metal surface layer are interposed between the bump electrodes and the silicon substrate. The

In the present invention, an iodine-based etching solution used for etching the base metal surface layer (gold or gold alloy) is preferably an aqueous solution of iodine and an iodine compound or a solution obtained by adding other components such as alcohol thereto. . Examples of the iodine compound include potassium iodide and ammonium iodide, and potassium iodide is preferred. Etching is usually performed by immersing the intermediate product of the semiconductor device after the plating resist layer is peeled and removed in an etching tank filled with an iodine-based etching solution. Etching conditions are not particularly limited, and examples include an immersion temperature of 20 to 30 ° C. and an immersion time of 0.1 to 10 minutes.
The etching of the base metal base layer can be performed using hydrogen peroxide water (for example, a concentration of 30% by weight) if the base metal base layer is a Ti / W layer. Although the etching conditions are not particularly limited, an immersion temperature of 30 to 50 ° C. and an immersion time of 3.0 to 20 minutes can be exemplified.

In the present invention, iodine and iodine compounds remaining on the surface of the semiconductor device after etching are cleaned and removed by a cleaning liquid containing thiosulfate.
Examples of the thiosulfate used in the cleaning liquid of the present invention include alkali metal salts such as sodium thiosulfate, potassium thiosulfate, and lithium thiosulfate, and ammonium thiosulfate, with sodium thiosulfate being preferred. The aqueous solution containing thiosulfate is prepared by dissolving thiosulfate in pure water.
The concentration of thiosulfate in the cleaning liquid of the present invention is preferably 0.5 to 10% by weight, more preferably 1.0 to 5.0% by weight, and still more preferably 2.0 to 4.0% by weight.
If the concentration of thiosulfate in the cleaning liquid is within the above range, secondary damage such as corrosion is not caused to the etched semiconductor device.

In the present invention, the amount of iodine and iodine compound remaining in the semiconductor device after cleaning varies depending on the number and shape of gold electrodes or gold wirings of the semiconductor device, but for example, the entire upper surface of a silicon wafer substrate having a size of 8 inches. When a semiconductor device having a gold electrode or a gold wiring is formed, the silicon wafer substrate on which the semiconductor device is formed is preferably 1 μg or less, more preferably 0.5 μg or less, and still more preferably 0 in terms of iodine per one wafer wafer. .2 μg or less.
The semiconductor device cleaned with the cleaning liquid is further put into a cleaning tank filled with ultrapure water, cleaned with ultrapure water, and dried to obtain the target semiconductor device. A semiconductor device (substrate) and ultrapure water (specific resistance 10 MΩ) are sealed in, heated in an oven at 75 ° C. for 1 hour, and air-cooled for 15 minutes, and then the amount of iodine is quantitatively analyzed by ICP-MS (ICP mass spectrometer). Is done in a way.

As a method of cleaning a semiconductor device having a gold electrode or a gold wiring formed with an iodine-based etching solution using the cleaning solution of the present invention, the semiconductor device is placed in a cleaning tank filled with the cleaning solution of the present invention. It is possible to exemplify a method in which iodine and iodine compounds are removed by washing, and then the semiconductor device after immersion is washed with ultrapure water and dried.
When cleaning a semiconductor device having a gold electrode or gold wiring formed with an iodine-based etchant, first, the gold or gold alloy on the base metal surface layer is etched and cleaned with ultrapure water, and then the base metal base layer Ti Examples include a method of etching an alloy or Ti, washing with ultrapure water, and finally washing with the cleaning liquid of the present invention. Also, the surface metal surface layer gold or gold alloy is etched and washed with ultrapure water, then washed with the cleaning liquid of the present invention, and then the base metal base layer Ti alloy or Ti is etched and washed with ultrapure water. If the concentration of thiosulfate in the cleaning solution is the same, the same effect can be obtained.

When the semiconductor device is cleaned using the cleaning liquid of the present invention, the immersion time in the cleaning tank can be appropriately changed depending on the shape of the semiconductor device, the state of stirring of the cleaning liquid, the temperature of the cleaning liquid, etc. The standard is a temperature of 20-30 ° C. and a cleaning time of 5-30 minutes.
The semiconductor device cleaned with the cleaning liquid is further placed in a cleaning tank filled with ultrapure water, immersed and washed at room temperature of 20-30 ° C. for 5-30 minutes under ultrapure water injection, dried by a spin dryer, A target semiconductor device is obtained, and a groove between the bump electrodes is filled with a thermosetting resin, cured and sealed, or formed into a desired dimension to be a final product.

Hereinafter, the cleaning liquid and the cleaning method of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
The sample used for the test was prepared by the following method.
[Preparation of cleaning test sample 1]
First, a silicon wafer (diameter: 200 mm) having a size of 8 inches is used as a substrate, a Ti / W (titanium / tungsten) layer (about 0.3 μm) as a base metal base layer thereon, and a gold layer (about 0.00 mm as a base metal surface layer). 2 μm) was formed in this order by the sputtering method. A plating resist layer is formed by a photolithography method on the surface of the base metal surface layer other than a region where a bump electrode is to be formed, and then a plurality (25 × 75 μm: 368640) is formed on the base metal surface layer by an electrolytic plating method. Gold bumps (plating thickness: about 15.0 μm) of pieces / wafer, 80 × 80 μm: 186240 pieces / wafer, a total of 554880 pieces / wafer) were formed. The shape of the gold bump is a substantially quadrangular prism having a rectangular cross section (25 × 75 μm or 80 × 80 μm), and the height in the vertical direction of the substrate is about 15.0 μm.
Next, the plating resist layer was peeled and removed by a method such as immersing in a peeling solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) heated to 40 to 100 ° C. for 5 to 30 minutes, and the base coated with the plating resist layer The substrate with the metal surface layer exposed is immersed in an etching bath (25 L Teflon bath) filled with an iodine-based etching solution (iodine 5 wt%, potassium iodide 10 wt%, methanol 74 wt%, pure water 11 wt%). Then, etching was performed at an immersion temperature of 23 ° C. and an immersion time of 1 minute to remove the base metal surface layer (gold layer). Next, this substrate was taken out and placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.), stirred at 23 ° C. under 5 L / min ultrapure water injection, and stirred by nitrogen bubbling. And then immersed in ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) and immersed in ultrapure water at 5 ° C / min for 10 minutes. After cleaning, the substrate is immersed in an etching tank (25 L Teflon tank) filled with hydrogen peroxide (31% by weight), etched at an immersion temperature of 43 ° C. and an immersion time of 12 minutes, and a base metal base layer (Ti / W layer) ) Was removed. Next, this substrate was taken out, placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.), stirred at 5 ° C. under 5 L / min ultrapure water injection, and stirred by nitrogen bubbling. After 10 minutes of immersion cleaning, it was placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) and immersed for 10 minutes at 23 ° C. under 5 L / min of ultrapure water injection. After washing, the sample was washed with a spin dryer to prepare a washing test sample.

[Preparation of cleaning test sample 2]
Preparation of cleaning test sample The substrate from which the base metal surface layer (gold layer) has been removed by etching 1 is placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) at 23 ° C. It was immersed in ultrapure water at 5 L / min and stirred for 10 minutes under nitrogen bubbling and washed in a washing tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.). After immersing and washing at 5 ° C. under 5 L / min ultrapure water injection for 10 minutes, the sample was dried by a spin dryer to prepare a sample for washing test.

[Observation of base metal base layer and measurement of width]
After the sample for cleaning test was washed with the cleaning liquids of Examples and Comparative Examples, the gold bump and the base metal surface layer (gold) of the sample were cleaned with iodine-based etching liquid (iodine 5 wt%, potassium iodide 10 wt%, Peeling was performed by immersing in a 25 L Teflon tank filled with methanol (74 wt%, pure water 11 wt%) at 23 ° C. for 6 hours. Next, the peeled surface was photographed with an electron microscope, the shape of the base metal base layer (Ti / W) under the 25 × 75 μm gold bump was observed, and the dimension in the width direction was measured by the method shown in FIG. During measurement, small pits due to erosion were ignored. Measurement was carried out at five locations on the wafer, and an average value, maximum value, and minimum value were obtained from the measurement values at five points.

Examples 1-4
Sodium thiosulfate pentahydrate (manufactured by Kanto Chemical Co., Inc.) was dissolved in pure water to prepare cleaning liquids having sodium thiosulfate concentrations as shown in Examples 1 to 4 in Table 1.
22 L of cleaning liquid having the composition shown in Table 1 was placed in a 25 L Teflon tank and heated to 23 ° C. The cleaning test sample (substrate) prepared in [Preparation of cleaning test sample 1] was immersed in this. The immersion time was 10 minutes, and then the substrate for cleaning test was taken out and placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) and injected with 5 L / min of ultrapure water at 23 ° C. After being immersed and washed for 10 minutes under stirring by nitrogen bubbling, it was further placed in a washing tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) at 23 ° C. and 5 L / min. After immersing and washing for 10 minutes under the injection of ultrapure water, it was dried with a spin dryer. The measurement of residual iodine after cleaning was carried out by enclosing a cleaning test sample (substrate) and 80 g of ultrapure water (specific resistance 10 MΩ) in an IC pack, heating in an oven at 75 ° C. for 1 hour, and air cooling 15 minutes later. Quantitative analysis of iodine was performed with MS (ICP mass spectrometer). The results are shown in Table 1. The results of Examples 1 to 4 and Comparative Example 1 (sodium thiosulfate concentration: 0) are shown in FIG. Moreover, the observation result of the base metal base layer of Example 4 and the measurement result of the width are shown in FIGS.

Examples 5 and 6
22 L of cleaning liquid having the composition shown in Table 1 was placed in a 25 L Teflon tank and heated to 23 ° C. The cleaning test sample (substrate) prepared in [Preparation of cleaning test sample 2] was immersed in this. The immersion time was 10 minutes, and then the substrate for cleaning test was taken out and placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.) and injected with 5 L / min of ultrapure water at 23 ° C. The sample was immersed and washed for 10 minutes under stirring by nitrogen bubbling, and then immersed in an etching tank (25 L Teflon tank) filled with hydrogen peroxide (31% by weight), soaking temperature was 43 ° C., soaking time was 12 Etching was performed in minutes, and the base metal base layer (Ti / W layer) was removed. Next, the substrate for cleaning test was taken out, placed in a cleaning tank filled with ultrapure water (specific resistance 10 MΩ, Sunny Trading Co., Ltd.), and immersed and washed at 23 ° C. under 5 L / min ultrapure water injection for 10 minutes. Then, it dried with the spin dryer. The amount of residual iodine after washing was measured in the same manner as in Examples 1 to 4. The results are shown in Table 1.

Comparative Examples 1-4
A cleaning solution was prepared in the same manner as in the example except that the chemicals and concentration of the cleaning solution were changed as shown in Comparative Examples 1 to 4 in Table 1, and the test was performed in the same manner as in the example (however, Comparative Example 4 was 70 ° C. To heat). The results are shown in Table 1. Moreover, the observation of the base metal base layer of Comparative Examples 1 and 2 and the measurement result of the width are shown in FIGS.

  From the results of Table 1, the cleaning liquids (Examples 1 to 6) of the present invention can remove iodine more effectively than the alkaline cleaning liquids of Comparative Examples 2 and 3. Further, as a result of confirming the presence or absence of damage to the Ti / W layer, as shown in FIG. 2, the cleaning liquid of the present invention (Example 4) has no corrosiveness to the Ti / W layer, and the alkaline cleaning liquid of Comparative Example 2 It was confirmed that the corrosion of the Ti / W layer was progressing. Further, as shown in FIG. 3, it was confirmed that the corrosiveness to the Ti / W layer was clearly smaller in the cleaning liquid of the present invention (Example 4) than in Comparative Example 2 using the alkaline cleaning liquid.

  Use for highly reliable semiconductor devices.

It is a figure which shows the sodium thiosulfate density | concentration of a washing | cleaning liquid, and the residual iodine amount per washing | cleaning test sample (wafer).

Etching the underlying metal surface layer of the cleaning test sample (substrate), immersing in the cleaning liquid of Table 1, drying, removing the gold bump and the underlying metal surface gold layer, and then Ti / W (titanium / tungsten) of the underlying metal base layer FIG. 2 is a diagram comparing the appearance of layers.

It is the figure which compared the dimension (average value, maximum value, minimum value) of the width | variety of the Ti / W (titanium / tungsten) layer of the base metal base layer of FIG. The vertical axis is the width dimension of the Ti / W layer (unit: μm)

It is an enlarged view of the left side sample of the comparative example 2 of FIG. 2 which shows the measuring method of the width | variety of a base metal base layer.

Claims (6)

  A cleaning solution for cleaning iodine and iodine compounds remaining in a semiconductor device having a gold electrode or a gold wiring formed by an iodine-based etching solution, wherein the cleaning solution is an aqueous solution containing thiosulfate .   The cleaning liquid according to claim 1, wherein the cleaning liquid contains 0.5 to 10% by weight of thiosulfate.   The cleaning liquid according to claim 1 or 2, wherein the thiosulfate is sodium thiosulfate.   A semiconductor device having a gold electrode or a gold wiring formed with an iodine-based etching solution is immersed in the cleaning solution according to any one of claims 1 to 3 to clean and remove residual iodine and iodine compounds, and then after immersion A cleaning method comprising cleaning a semiconductor device with ultrapure water.   A semiconductor device having a gold electrode or a gold wiring formed by an iodine-based etchant that is cleaned by the cleaning method according to claim 4.   The amount of iodine and iodine compound remaining in the semiconductor device is calculated in terms of iodine per 200 mm (8 inch) diameter silicon wafer substrate on which a semiconductor device having a gold electrode or gold wiring is formed on the entire upper surface of the silicon wafer substrate. The semiconductor device according to claim 5, wherein the semiconductor device is 1 μg or less.

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