JPH11293224A - Temporary adhesive for silicon wafer and purification of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temporary adhesive for silicon wafers, which is a rosin- based one, has a very low content of metallic ions and corrosive ions and affects semiconductor devices little and to provide a method for purifying the same. SOLUTION: There are provided a temporary adhesive for silicon wafers, comprising rosin, its derivative, a product obtained by modifying rosin with a dibasic acid, or a mixture thereof, and has a content of 10 ppb or below for each of sodium ion, calcium ion, magnesium ion, zinc ion, iron ion, copper ion, nickel ion, tin ion, lead ion, chromium ion, potassium ion, chloride ion, and sulfate ion, a content of aluminum ions of 20 ppb or below, and a total content of metallic ions of 50 ppb or below, and a process for purifying the same, comprising purifying a rosin by a combination of an acid extraction step with an ion exchange step to form a temporary adhesive for silicon wafers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temporary adhesive for silicon wafers, which is used for precision cutting, drilling, polishing, and the like.
The present invention relates to an adhesive useful for temporary attachment in various processes such as temporary attachment between a wafer and a surface plate.

[0002]

2. Description of the Related Art In the semiconductor industry, the pace of cost reduction and technological innovation is fast. For example, from the viewpoint of cost reduction, it is required to increase the diameter of a silicon wafer from 200 mmφ to 300 mmφ, which makes processing more difficult. Also, from the viewpoint of fine patterning, miniaturization of wiring patterns from 0.25 μm to 0.18 μm, and from the viewpoint of high density, high integration from 16 Mbits to 64 Mbits, respectively Directed technological development has been activated.

As described above, as the miniaturization of semiconductor devices progresses, various types of contamination (particles, metal ions, corrosive ions, organic substances, oxide films, etc.) have a great effect on the reliability and manufacturing yield of semiconductors. . Among them, the deterioration of device characteristics due to metal ion contamination has a problem of pn junction leakage, and the deterioration due to corrosive ions is large. Therefore, even in the case of a temporary adhesive for silicon wafers, the content of metal ions and corrosive ions is reduced, and a higher purity adhesive is required.

Conventionally, as a temporary bonding adhesive used for fusing a silicon wafer to a ceramic surface plate, an epoxy-based or acrylic-based synthetic resin-based material is used as a raw material monomer and synthetic resin from the viewpoint of low metal ion content. Although it has been proposed from the viewpoint that the demetalization process can be easily incorporated as a process, rosin-based temporary adhesives have been proposed because they are easy to balance in terms of performance such as bonding strength to silicon wafers, razor peelability, and cleaning properties. Is often used.

[0005] Natural rosin is obtained by extracting rosin with a solvent and then solidifying it in a warm bath. The rosin is composed of a mixture of various resin acids and is mainly composed of abietic acid having a conjugated double bond. Various modifications such as addition, esterification, polymerization, and maleation are possible, and have the advantage of easily matching the properties required as a temporary adhesive for silicon wafers. China is the largest producer of raw rosin (crude gum rosin) solidified in a warm bath after extracting rosin with a solvent, and is exported in zinc-coated drums.
Such raw rosin (crude gum rosin) contains a large amount of impurities, and domestic rosin manufacturers remove dirt, sand, metals, and the like by steam distillation, re-solvent extraction, or filtering. Rosin that has undergone such treatment is generally widely used as a printing ink material, and impurities such as metal ions are not considered to be a particular problem in this field, but contain metal ions at the level of several thousand ppb, Also,
Contains non-negligible corrosive ions. When such a rosin is used as a temporary bonding adhesive for a semiconductor wafer, in particular, metal ions such as Sn and nickel have a strong adsorptivity to a silicon wafer and cannot be completely washed, so that they are used as a temporary bonding adhesive for a silicon wafer. It is used by removing a part of metal ions by an ion exchange method or a chelate treatment method.

However, the removal rates of calcium ions, iron ions, aluminum ions and the like are poor depending on the ion exchange method or the chelating method, which is a usual demetalization ion method.
The total content of metal ion species normally contained in rosins is 5
At present, it is very difficult to reduce the value to 0 ppb or less.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a rosin-based temporary bonding adhesive, which has a very low content of metal ions and corrosive ions and has little influence on semiconductor devices. An adhesive and a method for purifying the same are provided.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the rosin-based temporary adhesive has a total metal ion content of 50 ppb or less and a corrosive ionic species. It has been found that it is possible to provide a temporary adhesive for silicon wafers and a purification method at a level that can be 10 ppb or less and does not affect the function of the semiconductor device.

The temporary adhesive for silicon wafers of the present invention is an aqueous alkaline solution-soluble adhesive used to temporarily temporarily adhere when processing a silicon wafer, and is a rosin or a derivative thereof or a rosin. Consisting of a modified form of dibasic acid alone or a mixture thereof, sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron metal ion, copper metal ion, nickel metal ion, tin metal ion, lead metal Ions, chromium metal ions, potassium metal ions, chloride ions, and sulfate ions each having a content of 10 ppb or less, an aluminum metal ion having a content of 20 ppb or less, and a total metal ion content of 50 ppb or less. Features.

The temporary adhesive for silicon wafers of the present invention may further contain 40% by weight of natural shellac or synthetic shellac.

[0011] The temporary adhesive for silicon wafers of the present invention may further contain a plasticizer.

The method of purifying a temporary adhesive for silicon wafers according to the present invention comprises dissolving rosin or a derivative thereof or a modified product of rosin dibasic acid alone or a mixture thereof in an aromatic hydrocarbon solvent, and then dissolving the mixture in an inorganic acid aqueous solution. , The organic phase is separated by an acid extraction treatment method, and the separated organic phase is purified by an ion-exchange method to obtain sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron metal ion. , Copper metal ion, nickel metal ion, tin metal ion, lead metal ion, chromium metal ion,
The content of each of potassium metal ion, chloride ion and sulfate ion is 10 ppb or less, the content of aluminum metal ion is 20 ppb or less, and the total content of metal ions is 50 ppb or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The rosins which are the main components of the adhesive include rosin, rosin ester, partially or hydrogenated rosin, polymerized rosin, or modified rosin of these rosin resins and dibasic acids such as maleic acid. At least one of their ester derivatives and the like is mentioned, and their acid value is 70.
mgKOH / g or more, which is soluble in an aqueous alkali solution. Examples of the rosins include those commercially available under the name of "Shiragiku Rosin" manufactured by Arakawa Chemical Industry Co., Ltd., "Foral AX" manufactured by Rika Hercules Co., Ltd., "Polyper Rosin", and "Pentalin 830". You.

The rosins in the present invention are purified by a purification method comprising an acid extraction treatment step and an ion exchange operation.

(1) In the acid extraction step, a commercially available rosin is dissolved in an aromatic hydrocarbon solvent such as toluene, xylene or benzene, preferably toluene, to give a 50% solution, and then 5% hydrochloric acid and sulfuric acid. An aqueous solution of an acid such as nitric acid is added to convert the metal ions into a colloidal precipitate, and then the aqueous phase having the colloidal precipitate is separated from the organic phase. After repeating this operation several times, wash with ultrapure water,
Next, the separated organic phase is dried to remove water.

By carrying out the acid extraction process at a liquid temperature of 20 ° C., 80% or more of sodium metal ions, calcium metal ions, zinc metal ions, tin metal ions, lead metal ions, and potassium metal ions can be removed. ,
Further, 60% to 80% of magnesium metal ion, aluminum metal ion, iron metal ion, copper metal ion and chromium metal ion can be removed. Further, a higher removal rate can be obtained by increasing the liquid temperature. However, in the acid extraction process, the removal rate of nickel metal ions is as low as 20% or less.
Corrosive ions such as chlorine ions and sulfate ions are not removed.

(2) Next, the organic phase obtained in the acid extraction treatment step is subjected to an ion exchange operation. The ion exchange operation is performed using a cation exchange resin ("Diaion PK228L" manufactured by Mitsubishi Chemical Corporation).
U ", a strongly acidic resin and a porous resin) and an anion exchange resin (" Diaion PA318 "manufactured by Mitsubishi Chemical Corporation).
1 (weight ratio) mixed product into a column (20 mmφ × 500 mm
H), and the organic phase obtained in the acid extraction step is passed through (3.3 g / min.).

By this ion exchange operation, 95% or more of sodium metal ion, zinc metal ion and iron metal ion, about 90% of magnesium metal ion and aluminum metal ion, calcium metal ion and copper metal ion contained in commercially available rosins. , Nickel metal ions, tin metal ions, lead metal ions, potassium metal ions, and chromium metal ions can be removed by nearly 100%, the amount can be traced, and the total metal ion content can be 50 ppb or less. In addition, the amount of corrosive ions such as chlorine ions and sulfate ions is also 90.
% Can be removed.

The temporary adhesive for silicon wafers of the present invention may contain natural shellac or synthetic shellac for the purpose of improving adhesiveness and melt viscosity. Examples of the shellac resin include natural shellac resin and synthetic shellac resin, and commercially available products such as "Product name, Shellac GS" manufactured by Gifu Cierac Co., Ltd. and "Product name, Shellac HK" manufactured by Koyo Chemical Co., Ltd. Acid value is 70mgKOH /
It is preferable to use an alkali-soluble substance having an amount of g or more. The shellac resin may be added in an amount of 40% by weight or less, preferably 5% by weight to 35% by weight, based on the rosin. However, if the amount is too large, the adhesiveness becomes strong and the melt viscosity becomes high. Not preferred.

Since the content of metal ions in the shellac resin is usually on the order of 2 × 10 ⁴ ppb,
It is preferable to perform a demetallization ion treatment by the same treatment method as that for rosins to set the order of 50 ppb or less.

Next, as the plasticizer, one or two or more selected from the group consisting of toluenesulfonic acid ethylamide, phthalic acid ester compounds, oxyacid ester compounds and aliphatic dibasic acid ester compounds are used. A mixture can be mentioned, and toluenesulfonic acid ethylamide is preferable. The plasticizer is added for the purpose of softening point, viscosity, and spreadability.
It may be added at a ratio of from 30% by weight to 30% by weight, but too much is not preferred because it becomes too soft.

The components such as rosin, shellac resin and plasticizer are used as a temporary adhesive for silicon wafers as a solution having a solid content of 20 to 50% by weight in an organic solvent such as isopropyl alcohol and toluene. .

The temporary adhesive for silicon wafers of the present invention contains rosin as a main component, and the adhesive as a whole has sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron The content of each of metal ions, copper metal ions, nickel metal ions, tin metal ions, lead metal ions, chromium metal ions, potassium metal ions, chlorine ions, and sulfate ions is 10 ppb or less, and the content of aluminum metal ions is 2 or less.
0 ppb or less, and the total content of metal ions is 50
ppb or less.

The temporary adhesive for silicon wafers of the present invention is applied onto a wafer or a surface plate by a spin coater method, a spray method, or the like, and after the solvent is removed, is heated and pressed, or the solvent is removed. The solid adhesive is melt-coated on the wafer or the surface plate, and then heated and pressed to securely fix the wafer on the surface plate. The wafer fixed in this way is subjected to polishing with an alkaline polishing liquid, and after the processing, the wafer is peeled off from the surface plate using a screver, a knife or the like.

The adhesive is required to bond and fix the wafer and the surface plate, to withstand the temperature rise of 40 ° C. to 50 ° C. and the alkali polishing solution during polishing, and to reach the mirror polishing, and to perform the polishing process. Later, for example, it is required that the blade of a razor be inserted into the bonding surface of the wafer and be peeled off at once, but in order to achieve both, the bonding strength is 25 kg.
/ Cm ^{2 to} about 35 kg / cm ² . The adhesive adhering to the peeled wafer is removed by performing primary cleaning with an alkaline cleaning agent and then performing a final rinse with pure water.

As the alkaline detergent, an aqueous solution of an organic amine such as tetramethylammonium oxide, alkanolamine, amino alcohol, or a water-soluble amine may be used, and it is preferable to avoid one containing metal ions.

[0027]

Next, the present invention will be described in detail with reference to examples and comparative examples.

(Example 1) (Acid extraction step) A 5% hydrochloric acid aqueous solution was added to 100 parts by weight of a 50% by weight toluene solution of rosin (“Foral AX” manufactured by Rika Hercules, Inc., acid value 160 mgKOH / g). After adding 5 parts by weight and stirring for 1 hour, the mixture was allowed to stand, and the aqueous phase in which the colloidal precipitate was dispersed was removed with a separating funnel. After this operation was repeated until the generation of colloidal precipitates was no longer observed, the organic phase was washed with ultrapure water, separated by a stationary liquid separation method and a centrifugal sedimentation method, and water was removed by a liquid separation method. .

(Ion exchange step) Next, a cation exchange resin ("Diaion PK228LU" manufactured by Mitsubishi Chemical Corporation)
And anion exchange resin (Mitsubishi Chemical Corporation “Diaion PA”
318 ") in a column (20 m
mφ × 500 mmH), and the organic phase obtained in the above-mentioned acid extraction step was passed (3.3 g / min.) at a conditioning condition of 2000 g / LR (8% hydrochloric acid).

(Evaluation method) The toluene solution before the treatment and the three kinds of treatment liquids obtained in the acid extraction step and the ion exchange step were each diluted with isopropyl alcohol so that the solid content was 30% by weight. The samples were subjected to quantitative analysis of their respective metal ion contents and corrosive ion contents.

(Analysis method) (1) Na, K, Mg, Cr, Fe, Ca, Ni, C
For each metal ion of u, Zn, and Al A sample was weighed in a platinum container and heated and ashed in an electric furnace (550 ° C.). This was treated with diluted hydrochloric acid and then dissolved in diluted nitric acid to make the volume constant.

The resulting solution was analyzed by atomic absorption spectrometry ("Polarized Zeeman atomic absorption spectrometer 180-8" manufactured by Hitachi, Ltd.).
0 ") by a flameless atomic absorption spectrometry (Hitachi, Ltd.," Polarized Zeeman atomic absorption spectrometer Z827 ").
0 ”), the measurement of K and Cu was carried out by ICP mass spectrometry (“ ICP mass spectrometer SPQ650 manufactured by Seiko Denshi Kogyo KK ”).
0 "), the measurement of Mg, Cr, Ni, Zn, Al
P emission spectroscopy (Sequential ICP emission spectroscopy SPS4000, manufactured by Seiko Denshi Kogyo KK)
Was used to measure Fe and Ca, and the content in the sample was determined.

(2) Regarding each metal ion of Pb and Sn A sample was weighed in a Teflon beaker, heated and decomposed with sulfuric acid, nitric acid and perchloric acid, and dissolved in dilute nitric acid to make a constant volume.

The solution was subjected to an ICP mass spectrometry (ICP mass spectrometer SPQ6 manufactured by Seiko Denshi Kogyo KK).
500 "), Pb and Sn were measured, and the content in the sample was determined.

Table 1 below shows the measurement results of the metal ion content of the sample before the treatment, the sample after the acid extraction step, and the sample that has undergone the acid extraction step and the ion exchange step. In the sample before the treatment, other metal ions are trace amounts.

[0036]

[Table 1]

The content is ppb. The removal rate in each step was determined by the following equation.

[0038] From Table 1, sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron metal ion, copper metal ion, nickel metal ion, tin metal ion, lead metal ion, chromium metal ion, potassium metal ion in rosins It can be understood that the content of each of chlorine, sulfate and sulfate ions can be 10 ppb or less, the content of aluminum metal ions can be 20 ppb or less, and the total content of metal ions can be 50 ppb or less.

(Preparation of Temporary Adhesive for Silicon Wafer)
3 parts by weight of toluenesulfonic acid ethylamide (Fujiamide Chemical Co., Ltd., Topsizer No. 3) was mixed with 60 parts by weight of the above-purified rosin 50% by weight toluene solution, and further, a mixed solvent {isopropyl alcohol / toluene (weight) Ratio) = 2/1｝ and 47 parts by weight,
A 0 wt% liquid temporary adhesive for silicon wafers was prepared.

Example 2 Rosin in Example 1 (“Foral AX” manufactured by Rika Hercules Co., Ltd., acid value 1)
Rosin (“Shiragiku Rosin” manufactured by Arakawa Chemical Industry Co., Ltd.) and an acid value of 165 mg KOH / g instead of 60 mg KOH / g).
g), and treated in the same manner, sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron metal ion, copper metal ion, nickel metal ion, tin metal ion, lead metal ion, chromium metal ion It was confirmed that the content of each of ions, potassium metal ions, chloride ions, and sulfate ions could be 10 ppb or less, the content of aluminum metal ions could be 20 ppb or less, and the total content of metal ions could be 50 ppb or less.

Comparative Example 1 A 50% by weight toluene solution of the rosin (“Foral AX” manufactured by Rika Hercules Co., Ltd., acid value 160 mg KOH / g) used in Example 1 was not subjected to the acid extraction step. The solution was passed through the same column as in Example 1 (3.3 g / min.).

(Evaluation method) The processing solution was prepared so that the solid content was 30% by weight.
Toluene / isopropyl alcohol (7 /
The sample was diluted with the mixed solvent of 3) to obtain a sample.
Each metal ion of Al, Fe, and Zn was measured as in Example 1.

Table 2 shows the results. The unit of the content is ppb.

[0044]

[Table 2]

If only the ion exchange method is used, Na, Al,
It can be seen that a large amount still remains even with the content of each metal ion of Fe and Zn alone.

Comparative Example 2 Rosin (Arakawa Chemical Industry Co., Ltd.)
“Shiragiku Rosin”, acid value 165mgKOH / g) 5
A 0 wt% toluene solution was used as a sample, and a column (20 mmφ
× 500 mmH) with a cation exchange resin ("Diaion PK228LH" manufactured by Mitsubishi Chemical Corporation, 50 ml-R), and the conditioning conditions were set to 2000 g / LR (8
% Hydrochloric acid). V (1.8 h ^-1 ).

Further, a cation exchange resin ("Diaion PK228LH" 50 ml-R manufactured by Mitsubishi Chemical Corporation) and an iminodiacetic acid type chelate resin ("CR11" 5 manufactured by Mitsubishi Chemical Corporation)
0 ml-R) and a column (20 mmφ × 5
00 mmH) and the conditioning condition was 20
At a flow rate of 00 g / LR (8% hydrochloric acid). V (1.8h
^-1 ).

(Evaluation Method) Each of the treatment liquids was dissolved in toluene / isopropyl alcohol (7%) so that the solid content became 30% by weight.
Each sample was diluted with a mixed solvent of (3)), and the respective contents of each metal ion of Na and Al were measured as in Example 1 as samples.

Table 3 shows the results. The unit of the content is ppb.

[0050]

[Table 3]

In the above table, for example, "0-5 L / LR
Indicates that, as the processing conditions, the sample was passed through the sample (0 L / LR) and then passed through a 5-fold volume (5 L / LR).

From Table 3, it can be seen that even when the ion exchange resin is changed or the chelating agent is changed, Na, Al
It can be seen that only a large amount of each metal ion remains.

[0053]

The temporary adhesive for silicon wafers of the present invention is an adhesive which has a very low metal content and corrosive ion content and is suitable for miniaturization of semiconductor devices, and a method for purifying the same.

Claims (4)

[Claims] An alkaline aqueous solution-soluble adhesive used for temporary attachment during processing of a silicon wafer, wherein the adhesive is rosin or a derivative thereof or a modified product of rosin dibasic acid alone or It consists of its mixture, its sodium metal ion, calcium metal ion, magnesium metal ion, zinc metal ion, iron metal ion, copper metal ion, nickel metal ion, tin metal ion, lead metal ion, chromium metal ion, potassium metal ion, The content of each of chloride ion and sulfate ion is 10 ppb or less, and the content of aluminum metal ion is 2
0 ppb or less, and the total content of metal ions is 50
A temporary adhesive for silicon wafers having a ppb or less. 2. The temporary adhesive for silicon wafers according to claim 1, further comprising natural shellac or synthetic shellac at a ratio of 40% by weight or less. 3. The temporary adhesive for silicon wafer according to claim 1, further comprising a plasticizer. 4. A solution of rosin or a derivative thereof or a modified product of rosin dibasic acid alone or a mixture thereof in an aromatic hydrocarbon solvent, and then adding an inorganic acid aqueous solution, separating the organic phase by an acid extraction treatment method. And further, the separated organic phase is purified by an ion exchange method using a mixed resin of a cation exchange resin and an anion exchange resin, and its sodium metal ion, calcium metal ion, magnesium metal ion,
The content of each of zinc metal ion, iron metal ion, copper metal ion, nickel metal ion, tin metal ion, lead metal ion, chromium metal ion, potassium metal ion, chloride ion, and sulfate ion is 10 ppb or less. A method for purifying a temporary adhesive for silicon wafers, wherein the content is 20 ppb or less and the total content of metal ions is 50 ppb or less.