JPH1096685A - Method for evaluating adhesion amount of particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating an adhesion amount of particles as an adhesion index of particles in a development of a wet surface treatment liquid such as a cleaning liquid, an etching liquid or the like for semiconductor wafers. SOLUTION: A measurement material coated to a quartz vibrator by CVD or sputtering is immersed in a solution, and an adhesion amount of particles during a surface treatment such as cleaning or the like is obtained by monitoring a change of a resonant frequency of the quartz vibrator. The quartz vibrator coated with the measurement material is incorporated in a flow cell, and measured while factors of the solution, e.g. a temperature, a pH, a fluid state, etc., are controlled. The flow cell is constituted so that the solution becomes a laminar flow by securing a flow path of a uniform thickness above the quartz vibrator coated with the measurement material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a particle adhesion amount as an index of particle adhesion in the development of a wet surface treatment liquid such as a cleaning liquid or an etching liquid for a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, the amount of particles attached to a wafer by wet surface treatment such as cleaning of a semiconductor wafer has been measured by a surface foreign particle meter. The surface foreign particle meter is a method of irradiating a laser beam on the wafer surface and measuring the number of adhered particles from the scattering state. However, the minimum diameter of the particles that can be detected by this method is about 0.17 μm.
It is expected that smaller particles will become a problem as the degree of integration increases in the future, but there is no suitable method for measuring the amount of particles attached to 0.1 μm or less. Further, in such an optical means, measurement in the cleaning liquid is impossible, and the measurement must be performed after the wafer is once taken out of the cleaning liquid and dried. It is known that the amount of adhered particles greatly depends on the temperature, pH, flow state and the like of the cleaning liquid, but the conventional method cannot measure the amount of adhered particles while controlling such factors. Therefore, there is very little systematic knowledge on the particle adhesion behavior that can be a guide for the design of a wet surface treatment solution such as a cleaning solution, and the design of a cleaning solution is largely a matter of trial and error.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a method capable of measuring and evaluating the amount of attached particles to a small diameter in a liquid.

[0004]

According to the method of the present invention for solving the above-mentioned problems, a measuring material coated on a quartz oscillator by a CVD method or a sputtering method is immersed in a solution and subjected to surface treatment such as washing. The amount of particles attached in the process can be obtained by monitoring the change in the resonance frequency of the quartz oscillator. In addition, a quartz resonator coated with the measurement material is incorporated into the flow cell, and the temperature, pH, flow state, etc.
This is a method in which measurement can be performed by controlling factors on the solution side. The flow cell is configured such that the solution has a laminar flow by securing a flow path having a uniform thickness on the quartz resonator coated with the measurement material.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A quartz oscillator incorporated in a resonance circuit has an oscillation frequency (f) perpendicular to the thickness direction.
_Resonates at ₀ ). At this time, when the measurement material coated on the crystal unit comes into contact with the solution and the mass increases due to the adhesion of particles, a change in resonance frequency (Δf) occurs. The relationship between Δf and the number of attached particles (N) is often given by the following equation. N = -Δf / {[2 ( 4/3) πa 3 ρ P / (ρμ) 1/2] f 0 2 + 6a 2 [πη L ρ L / (ρμ)] 1/2 · [1+ (2/9 ) (A / δ)] f ₀ ^3/2 ｝ (1) δ = (η _L / ρ _L πf) ^1/2 (2) where f: resonance frequency N: number of attached particles per unit area ρ _P : Particle density a: Particle radius
η _L : solution viscosity ρ _L : solution density μ: crystal oscillator elastic modulus ρ: crystal oscillator density.

[0006] Even when the above equation does not hold, N and Δf
Are in a proportional relationship. Therefore, by continuously monitoring the resonance frequency change Δf, the number of attached particles can be measured in real time.

[0007]

【Example】

(Example 1) Si was deposited on an electrode of a quartz oscillator at 5000 ° by sputtering, and then S was deposited by sputtering.
An TiO ₂ film was deposited to a thickness of 2000 °. With this method, a SiO ₂ film could be formed on the quartz oscillator with good adhesion. This crystal oscillator is incorporated in a flow cell and the pH is 1
An aqueous HCl solution adjusted to be circulated in the flow cell was circulated at a flow rate of 4.3 cm / s. When the frequency became stable, standard polystyrene latex particles having a diameter of 0.1 μm were added. Δf increased with time. After measuring Δf, the surface of the SiO ₂ film on the quartz oscillator was observed with an electron microscope, and the relationship between the number of attached particles and Δf was examined. The relationship was proportional, and the slope was calculated from equations (1) and (2). Value. (See FIG. 1) (Example 2) An SiO ₂ film was formed on a quartz oscillator with good adhesion by the same method as in Example 1. This crystal oscillator was incorporated in a flow cell, and H adjusted to pH 1 was obtained.
Cl aqueous solution and NaO adjusted to pH 7
An H aqueous solution was circulated at a flow rate of 4.3 cm / s, and an adhesion evaluation experiment of polystyrene latex standard particles was performed in the same manner as in Example 1. Δf was larger at pH 1 and at pH 7, Δf hardly changed (see FIG. 2). From this, it was found that the pH of the cleaning solution of 7 was less likely to cause particle adhesion than the cleaning solution of the pH of 1.

[0008]

According to the present invention, it is possible to evaluate the amount of particles attached to a solution to a small diameter in a solution, and to evaluate the solution while controlling the flow, pH, etc. of the solution. It is extremely useful.

[Brief description of the drawings]

FIG. 1 is a graph showing the quantification of the present invention, showing the relationship between the resonance frequency change Δf and the number of adhered polystyrene latex standard particles (PSL).

FIG. 2: pH of the cleaning solution for the attachment of PSL to SiO ₂
FIG.

Claims (2)

[Claims] 1. A quartz crystal resonator is coated with a material to be measured constituting a semiconductor element, the measured material is brought into contact with a solution, and the quartz crystal resonator is vibrated by a transmitter. A method for evaluating the amount of adhered particles, characterized by quantitatively evaluating the amount of adhered particles to a material. 2. A quartz oscillator coated with a material to be measured constituting a semiconductor element is incorporated in a flow cell, and the solution is caused to flow into the flow cell so that the material to be measured is brought into contact with the solution and vibrated by a transmitter. A method for evaluating the amount of attached particles, characterized by quantitatively evaluating the amount of attached particles to a material to be measured in a solution from a change in the resonance frequency of a vibrator.