JPH047830A - Chemical for cleaning surface of semiconductor wafer - Google Patents

Abstract

PURPOSE:To remove completely a chemical for cleaning absorbed on a wafer surface by a rinsing using pure water and to prevent a contaminated substance from being readhered on the wafer surface after the rinsing by a method wherein a polymer electrolyte is added to the chemical for wafer surface cleaning. CONSTITUTION:A polymer electrolyte is added to a liquid for wafer surface cleaning use. For example, an anionic polymer electrolyte like a copolymer obtainable by polymerizing an acrylic acid and styrene is added to an alkaline surface treatment cleaning liquid. At this time, the degree of dissociation of the electrolyte is high, a polymer chain is brought into a state that it is loosely spread by electrolytic repulsion between carboxylate anions 2b, these anions 2b are turned to the side of a solution, hydrophobic groups 2c are brought into a state that they are absorbed on a wafer surface 1a and the surface 1a is covered with the groups 2c. When the wafer surface 1a is rinsed with pure water after being cleaned, the degree of dissociation of the electrolyte absorbed on the surface 1a is reduced by a change of a pH into the neutral region of the pure water, the polymer chain is shrinked and the polymer electrolyte is peeled from the surface 1a. Thereby, a chemical for cleaning use absorbed on the wafer surface 1a is completely removed by the rinsing using the pure water and a contaminated substance can be prevented from being readhered on the wafer surface after the rinsing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a chemical solution used in a semiconductor wafer manufacturing process and surface treatment during device formation, particularly in cleaning treatment.

[Conventional technology]

Figure 5 shows the surfactant 5 added to the cleaning chemicals used to conventionally clean the surfaces of semiconductor wafers.
This is a schematic diagram showing one molecule of , and in the figure, 5a is a polar or ionic hydrophilic group, and 5b is a hydrophobic group consisting of a molecular chain such as an alkyl group.

FIG. 6 is a diagram of the vicinity of the wafer in the chemical solution to which the surfactant 5 is added, where lb is the cross section of the semiconductor wafer,
1a shows its surface.

When the surfactant 5 as described above is added to a chemical solution for cleaning the surface of a semiconductor wafer, the surface tension of the chemical solution decreases, and as shown in FIG. is adsorbed onto the surface 1a of the semiconductor wafer toward the solution side, thereby uniformly treating the wafer surface and preventing contaminants from re-adhering.

[Problem to be solved by the invention]

The cleaning chemical solution used in conventional semiconductor wafer surface cleaning is structured as described above, and since the surfactant is adsorbed to the wafer surface with its hydrophobic groups, it is difficult to completely remove the surfactant by rinsing with pure water. Some of it remains on the wafer surface, and the polar or ionic hydrophilic groups attract contaminants. Also, since surfactants are foaming agents, they are difficult to clean during the cleaning process. There were problems such as the in-plane uniformity of the surface treatment being disturbed due to the bubbles generated.

This invention was made to solve the above-mentioned problems, and it improves the wettability of the semiconductor wafer surface, making it possible to process it uniformly. The purpose of the present invention is to obtain a chemical solution for cleaning the surface of a semiconductor wafer that can completely remove contaminants and prevent re-adhesion of contaminants after rinsing.

[Means to solve the problem]

The semiconductor wafer surface cleaning chemical solution according to the present invention is a surface cleaning chemical solution containing an acid or a base as a main component to which a polymer electrolyte is added.

[Effect]

In invention 2, since a polymer electrolyte is added to a surface cleaning chemical solution containing an acid or a base as a main component, the polymer electrolyte adsorbed on the wafer surface undergoes a shape change by rinsing with pure water, and is peeled off from the wafer surface. However, there is no residual electrolyte on the surface, and no persistent bubbles are generated like surfactants.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows a schematic diagram in which a copolymer of acrylic acid and styrene is used as the polymer electrolyte 2 added to a chemical solution for cleaning the surface of a semiconductor wafer according to an embodiment of the present invention.
In the figure, 2a is a carboxyl group which is a hydrophilic group, 2b
This is a carboxylate anion in which the carboxyl group 2a is dissociated, and 2C is a phenyl group which is a hydrophobic group.

It is generally known that polymer electrolytes change their form as the degree of dissociation changes depending on the pH of a solution containing them. Figure 3 (Baifukan “Science of Polymers-IP.

To explain in detail using (quoted from 91), 3 a +
31-1.3c are polymethacrylic acid (PMAA), respectively.
)3 Polyacrylic acid (FAA, ), Methacrylic acid (MA
The relationship between the degree of dissociation α and pH in A) is shown. Polyelectrolytes PMAA, 3a, PA, and A3b undergo morphological changes at bending points 3d and 3d', respectively, and 3f shows that the polyelectrolyte chain changes. 3e indicates a region where the chain exists in a compactly contracted form, and 3e indicates a region where the chain exists in a loosely extended form.

Taking advantage of this morphological change, in the case of the anionic polymer electrolyte 2 such as the copolymer of acrylic acid and styrene, a high pH range, that is, an alkaline solution is used as the surface treatment cleaning solution. At this time, as shown in Figure 1, the degree of dissociation of the polymer electrolyte is high, and the electrostatic repulsion between the carboxylate anions 1b causes the polymer chains to spread loosely, directing the anions 1b toward the solution side. The hydrophobic groups 1c become adsorbed to the wafer surface 1a and cover the wafer surface.

Therefore, it is possible to process the wafer uniformly within the wafer surface while preventing re-adhesion of contaminants.

After cleaning, when rinsing with pure water, the pH of the polymer electrolyte 2 adsorbed on the wafer surface changes from the high pH region of the cleaning solution to the neutral region of the pure water, resulting in a small degree of dissociation (the anion lb The electrostatic repulsion between them is softened, and conversely, due to the interaction between adjacent hydrophobic groups 10, the polymer chains try to contract, and as a result, the polymer electrolyte 2 is separated from the wafer surface, leaving a perfect wafer surface condition. can be formed.

Additionally, polyelectrolytes do not produce persistent foam like surfactants.

In the above example, an anionic polymer electrolyte was used, but if a cationic polymer electrolyte is used, the surface treatment cleaning chemical should be in the low pH 9I range, that is, acidic. A similar effect can be achieved with

As described above, according to this embodiment, instead of a surfactant, polymer electrolyte 2 is added to the chemical solution for cleaning the wafer surface.
Since wafers are cleaned by utilizing the morphological changes associated with changes in the degree of dissociation caused by H, there is no persistent bubbles produced like with surfactants, and it is compatible with any surface cleaning chemical solution. Even for wafers, the inner surface can be uniformly processed, and cleaning chemicals adsorbed on the wafer surface can be completely removed by rinsing with pure water, thereby preventing contaminants from re-adhering after rinsing.

〔Effect of the invention〕

As described above, according to the semiconductor wafer surface cleaning chemical solution according to the present invention, since a polymer electrolyte is added to the wafer surface cleaning solution, the surface tension of the chemical solution is reduced and the wettability of the wafer surface is increased. In addition to being able to uniformly process the wafer, the adsorbed polymer electrolyte can be completely removed by rinsing with pure water, resulting in the formation of a perfect wafer surface.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the adsorption state of a polymer electrolyte used in a chemical solution for semiconductor wafer surface cleaning according to an embodiment of the present invention to the wafer surface, FIG. 2 is a schematic diagram of its dissociation, and FIG. is a diagram to explain the properties of polymer electrolytes,
FIG. 4 is a schematic diagram of a polymer electrolyte used in a chemical solution for cleaning the surface of a semiconductor wafer according to an embodiment of the present invention, FIG. 5 is a schematic diagram of a surfactant used in a conventional chemical solution for cleaning the surface of a semiconductor wafer, and FIG. FIG. 6 is a schematic diagram showing how a surfactant used in a conventional semiconductor wafer surface cleaning chemical is adsorbed onto the wafer surface. In the figure, 1 is a semiconductor wafer, 1a is a semiconductor wafer surface, 1b is a cross section of the semiconductor wafer, 2 is a polymer electrolyte, and 2a is a semiconductor wafer surface.
is a carboxyl group, 2b is a carboxylate anion,
2C is a phenyl group. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A chemical liquid for cleaning the surface of a semiconductor wafer, characterized in that a polymer electrolyte is added to the chemical liquid for cleaning the surface of a semiconductor wafer.