JPS6314038B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to the composition of a cleaning liquid, and particularly to a cleaning liquid suitable for substrate pretreatment before forming a thin film. [Technical background of the invention and its problems] Conventionally, as cleaning liquids for substrate pretreatment, organic,
Acid or alkaline substances are used. An alkaline cleaning solution, especially for cleaning silicon wafers, is called SC-1 and contains 1.5 to 2.3 [mol] of ammonia and 1.5 to 1.5 [mol] of hydrogen peroxide per 1 [] of water.
It is known that a cleaning solution with a composition of 2.2 [mol] is superior. However, this cleaning solution
If amphoteric elements or metals such as aluminum are present on the substrate, these will be attacked. for example,
If the thickness of aluminum is 1 [μm], it may melt in a few seconds. Furthermore, in the case of other alkaline and acidic systems, amphoteric elements, metals, etc. may be attacked in the same way. Therefore, for example, if metal is present on the substrate, a cleaning liquid must be selected that does not have a corrosive effect on the metal. For this reason, it is necessary to prepare cleaning liquids suitable for various cases, and a wide variety of cleaning liquids are required, which tends to complicate the handling of waste liquid and post-treatment of the cleaning liquid, which also poses a problem in terms of cost. Furthermore, when there are various kinds of metals on the substrate, there is currently no alkaline or acid-based cleaning solution that can clean them without damaging any of them. On the other hand, organic cleaning liquids do not attack the metals mentioned above, but the residue of the cleaning liquid adheres to the substrate. This residue causes defects during thin film production as blue residue and pinholes, so
The residue needs to be removed. However, there are drawbacks in that many processes are required to remove the residue of the organic cleaning solution, and the residue cannot be reliably removed even after thorough cleaning. [Object of the invention] The present invention has been made in consideration of the above circumstances, and
The purpose of this is that the rate of attack on amphoteric elements such as aluminum and metals on the substrate is extremely slow, and the residue does not adhere to the substrate.
Another object of the present invention is to provide a cleaning liquid having high cleaning power. [Summary of the Invention] The gist of the present invention is to use an alkaline cleaning liquid and to suppress the corrosive effect of this cleaning liquid on metals. That is, the present invention provides a cleaning solution used for substrate pre-treatment etc. whose composition is 1 [] of water;
Hydrogen peroxide 0.9 to 3.8 [mol] preferably 1.5 to 2.0
[mol], at least one selected from ammonium salts 0.1 to 2.5 [mol], preferably 0.3 to 1.5 [mol],
Also, if necessary, it is made to contain 2.5 [mol] or less of ammonia. In the present invention, the ammonia water and hydrogen peroxide water produced from ammonia or ammonium salts sterilize and remove bacteria, etc., and remove organic deposits, and also remove trace amounts of impurity metals that are oxidized by hydrogen peroxide and dissolved in the ammonia water. remove. For example, when the substrate to be cleaned is glass, ammonia water generated from ammonia or ammonium salts can be used to thinly attack the surface of the glass, thereby removing deposits that are strongly adsorbed to the glass, leaving the glass surface smooth and clean. Make a good surface. Further, the ammonia water makes the cleaning solution alkaline and prevents breakdown of the insulator. Furthermore, the ammonium salt acts as a PH buffer for the washing solution and contributes to the stabilization of the washing solution. Anions such as inorganic oxides and surfactants in the ammonium salt selectively remain in the fixed layer of the electric double layer in the cleaning solution on the metal surface of the substrate, thereby protecting the metal surface and reducing its corrosion rate. suppress. Furthermore, when ultrasonic waves are applied during cleaning, mechanical cleaning is added due to the effects of oxygen bubbles from hydrogen peroxide, etc., making it possible to increase the degree of cleaning. Furthermore, better cleaning power can be obtained by raising the liquid temperature to 70 to 85 [°C]. Here, the concentration of ammonium salt with respect to 1 [mol] of water is 0.1 to 2.5 [mol], and the reason is 0.1 [mol]
If it is less than that, the above-mentioned effects of stabilizing the cleaning liquid and suppressing the corrosion rate of metal will hardly be achieved. Furthermore, if the amount is 2.5 [mol] or more, it will itself contaminate the cleaning solution, resulting in residues and the like. Further, the concentrations of ammonia and hydrogen peroxide need to be within the ranges mentioned above in order to make the cleaning solution weakly alkaline. In addition, when ammonia is not used, the preferred concentration of hydrogen peroxide is 1.5 to 2.0 [mol], and the concentration of ammonium salt is 0.3 to 1.5 [mol], but when ammonia is used, the concentration range above depends on the amount of ammonia. will shift slightly in the lower direction. [Effects of the Invention] According to the cleaning liquid of the present invention, the following effects can be obtained. Due to the protective action of anions such as inorganic oxides or surfactants in the ammonium salt, it is difficult to attack amphoteric elements such as aluminum and other metals. The cleaning liquid has a pH of 7.5 to 8.0 and is weakly alkaline, so there is no risk of attacking oxide films on ceramic substrates, insulators, and semiconductor wafers, and it exhibits excellent cleaning power, especially on glass substrates. It is extremely reliable because it does not contain any metal ions that are harmful to semiconductor processes. (4) Even though hydrogen peroxide is used for metals that are easily oxidized, the metal surface after cleaning treatment is not oxidized and a clean cleaned surface can be formed. (5) Compared to other cleaning liquids (especially organic cleaning liquids), many processes are not required for post-cleaning treatment, and the cleaning liquid can be easily removed by methods such as pure spraying after cleaning. (6) Since no special chemicals are used, it is advantageous in terms of cost. [Examples of the Invention] The details of the present invention will be explained below with reference to Examples. <Example 1> A glass substrate on which chromium and aluminum were individually vacuum-deposited was subjected to ultrasonic cleaning at a temperature of 75±5 [° C.] using a cleaning solution having a composition shown in Table 1 below.

[Table] Here, the concentration of ammonia water is 28%,
The hydrogen peroxide solution used had a concentration of 35%. Note that the right column of Table 1 shows the respective molar concentrations of ammonia, ammonium phosphate, and hydrogen peroxide with respect to water 1[]. Further, the cleaning liquid having the above composition had a pH in the range of 7.5 to 8 and was weakly alkaline. As a result of this experiment, the aluminum film thickness was 1 [μm]
This cleaning solution can be used after penetration time of about 15 minutes or less, and sufficient cleaning treatment can be performed within this time. Furthermore, it was found that even in subsequent thin film formation, good conditions were obtained, with no blue residue or pinholes occurring. The composition shown in Table 1 is the same as the conventional cleaning liquid SC-1 except for ammonium phosphate, but
In SC-1, 1 [μm] of aluminum was melted in a few seconds. This shows that the addition of ammonium phosphate can sufficiently suppress the corrosion effect of aluminum. <Example 2> Similar to Example 1, chromium and aluminum were individually vacuum-deposited on a glass substrate, and the following
Using a cleaning solution with the composition shown in the table, the temperature is 75 ± 5 [℃].
Ultrasonic cleaning was performed. The concentration of the hydrogen peroxide solution was the same as in the previous example, and the molar concentration was also written in the right column of Table 2 as before.

[Table] As a result of this experiment, the aluminum film thickness was 1 [μm]
It was found that this cleaning solution can be used after a penetration time of about 20 minutes or less, and that good conditions can be obtained even in subsequent thin film formation. Note that the present invention is not limited to the embodiments described above. For example, as the ammonium salt, in addition to ammonium phosphate, at least one selected from ammonium citrate, ammonium acetate, ammonium silicate, and other ammonium salts having inorganic oxide anions is used. be able to. Furthermore, its concentration is 1
[ ] can be changed as appropriate within the range of 0.1 to 2.5 [mol]. In addition, the concentrations and amounts of ammonia water and hydrogen peroxide solution are not limited to those in the examples in any way, and in short, it is sufficient as long as the concentration of ammonia and hydrogen peroxide in the cleaning solution falls within the above-mentioned range. . Moreover, it goes without saying that ultrasonic cleaning is not always necessary, and that the temperature during cleaning is not limited to 75±5 [° C.] and can be changed as appropriate.
In addition, various modifications can be made without departing from the gist of the present invention.

Claims (1)

[Claims] 1. In a cleaning solution for cleaning the surface of a substrate on which a metal layer is formed before a thin film forming process, water 1[]
2.5 [mol] or less of ammonia, hydrogen peroxide
A cleaning solution containing 0.9 to 3.8 [mol] and 0.1 to 2.5 [mol] of at least one selected from ammonium salts. 2. Claim 1, wherein the ammonium salt is an ammonium salt having ammonium phosphate, ammonium citrate, ammonium acetate, ammonium silicate, and other inorganic oxide anions. Cleaning liquid as described in section. 3. The cleaning liquid according to claim 1, wherein 2 to 50 [g] of a nonpolar or negatively charged surfactant is further added to 1 [] of the water. 4 In the cleaning solution for cleaning the surface of the substrate on which the metal layer is formed before the thin film formation process, water 1[]
0.9 to 3.8 [mol] of hydrogen peroxide, and 0.1 to 2.5 [mol] of at least one selected from ammonium salts.
cleaning solution containing. 5. Claim 4, characterized in that the ammonium salt is an ammonium salt having ammonium phosphate, ammonium citrate, ammonium acetate, ammonium silicate, and other inorganic oxide anions. Cleaning liquid as described in section. 6. The cleaning liquid according to claim 4, wherein 2 to 50 [g] of a nonpolar or negatively charged surfactant is further added to 1 [] of the water.