JPH02224243A - Cleaner and cleaning degree measuring method - Google Patents

Abstract

PURPOSE:To enable cleaning degrees of plural times to be measured independent of the change of circumstance of cleaning process by using at least one exo- electron detector which is arranged in the specified position inside a cleaner. CONSTITUTION:A semiconductor substrate 11 is attached to a holder 10, and makes a round of each chemical bath 1-8 and is soaked in chemical for cleaning for a certain time. As chemical solution 9, for example, pure water for a bath 1, and acetone solution, trichloroethylene solution, acetone solution, nitric acid solution, pure water, hydrofluoric acid solution, and pure water are used in this order. While the semiconductor substrate 11 is shifting each bath, exo- electrons are measured in the middle by a detector 12, an electronic calculator 13 and an ammeter 14 so as to measure the cleaning degrees. Hereby, the cleaning degrees of the semiconductor substrate can be measured at several stages independent of the change of outside circumstance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cleaning device and a cleaning degree measuring method.

In conventional methods of manufacturing semiconductor devices, semiconductor substrate processing is generally performed.

Examples of such processing include crystal growth technology, impurity diffusion technology, passivation film growth technology, heat treatment accompanied by reaction such as metallization technology, and fine etching technology such as photoresist processing technology applied to the substrate surface, wet etching, and dry etching technology. Processing technology is combined.

Furthermore, each processing technology process includes a cleaning process and a drying process to keep the substrate clean.

The yield of semiconductor devices is largely determined by the amount of foreign matter in the atmosphere during the manufacturing process. For this reason, it is important to have techniques for processing and handling the substrate in an atmosphere where the amount of foreign matter is sufficiently controlled.

Sources of foreign matter include human-generated sources, semiconductor processing equipment, gases used, chemicals used, high-purity water used, and the like.

However, it is important to control the cleanliness of the substrate because the substrate must be cleaned every time it is soaked during various processes.

In the conventional technology, the level of cleanliness is ensured by cleaning the substrate to remove human-generated dust and floating dust generated from semiconductor processing equipment.

Normally, in cleaning methods for semiconductor substrates, detailed cleaning steps are performed under certain cleaning conditions, and the cleaning state is not observed during the cleaning process. It was necessary to take them out of the cleaning equipment and observe them individually.

Auger electron spectroscopy and photoelectron spectroscopy are methods for examining the cleaning state of semiconductor substrates taken outside.

In either case, emitted electrons from the surface of the material carry energy information unique to the material, and qualitative or quantitative chemical analysis is performed by measuring the energy of the electrons and the amount of emitted electrons generated.

Problems to be Solved by the Invention However, in a normal semiconductor substrate cleaning process, when the semiconductor substrate is taken out of the cleaning device and observed using conventional methods, that is, microscopic observation, dust measuring equipment, Auger electron spectroscopy, or photoelectron spectroscopy,
Semiconductor substrates can become contaminated when exposed to outside air, moved by people, or brought into equipment, so the cleaning status is often not checked before proceeding to the next process, so it is difficult to determine how the cleaning level will affect the semiconductor substrate. In order to know whether the cleaning process is complete or not, it must be evaluated only after the entire cleaning process has been completed.

Furthermore, in Auger electron spectroscopy and photoelectron spectroscopy, the sample must be destroyed during measurement, and the sample surface changes during analysis, resulting in low reliability of the sample.

Means for solving the problem include developing at least one exoelectronic detector installed at a predetermined location within the cleaning device.

Further, a first step of inserting an exoelectron detector installed in a non-contact with the semiconductor substrate into the cleaning device, a second step of cleaning the semiconductor substrate, and a point where the amount of exoelectrons reaches a predetermined amount. and a third step of taking it out from the cleaning device.

Operation By adopting this principle, the present invention makes it possible to observe the cleanliness of a semiconductor substrate as a change in exoelectrons depending on a change in the state of the surface of the substrate.

What can be measured as exoelectrons makes it possible to observe the surface using information on the state of the surface of a material and changes in that state, which is different from Auger electron spectroscopy or photoelectron spectroscopy.

In addition, the surface cleanliness was measured on the semiconductor surface.
Observation of the cleanliness of the surface is generally done during the cleaning process, but if the environment changes, the cleanliness cannot be measured correctly.
In the present invention, since the cleanliness measuring device is installed integrally inside the cleaning device, the cleanliness of the semiconductor surface can be measured multiple times without changing the environment of the cleaning process.

If the degree of cleanliness is measured by taking the substrate out of the cleaning device as in the past, it is also possible to measure the degree of cleanliness of contamination caused by taking it out.

Example FIG. 1 shows an outline of a mechanism according to an embodiment of the present invention.

Semiconductor substrate cleaning (chemical) tank 1, 2, 3, 4, 5°6.7
．． A substrate holder 10 and a semiconductor substrate 11 are arranged on the upper part of the cleaning tank 8 in order to expand to each cleaning tank.

Semiconductor substrate cleaning (chemical) tank used 1.2, 3°4.5.
The size of 6.7.8 is 30 am long x 30 QIIX wide.
The depth is 30a11, and the material is selected so that it does not change depending on the chemicals used. For example, quartz material was used for water washing, quartz material was used for acetone/trichlorethylene, quartz material was used for nitric acid treatment, and polybrolethylene material was used for hydrofluoric acid treatment.

Functionally, the 5-inch silicon substrate 11 can be cleaned, and the holder 10 made of polypropylene material can be thoroughly cleaned after installing the silicon substrate, so that various operations can be performed automatically without manual labor. It's Nishide.

The semiconductor substrate 11 is mounted on a holder 10 and inserted into the chicken product for cleaning around each chemical bath 1 to 8 for a predetermined period of time. Here, as the chemical solution 9, in the tank 1, pure water,
An acetone solution was used in tank 2, a trichlorethylene solution in tank 3, an acetone solution in tank 4, a nitric acid solution in tank 5, pure water in tank 6, a hydrofluoric acid solution in tank 7, and pure water in tank 8.

While the semiconductor substrate 11 moves within each tank, a detector 12, an electronic counting device 13, and an ammeter 14 are installed along the way.
The degree of cleanliness is measured by measuring exoelectrons.

In other words, in commonly used chemical analyzes such as Auger electron spectroscopy and photoelectron spectroscopy, the surface of a solid, such as a metal surface or a semiconductor surface, is exposed to electromagnetic waves such as ultraviolet rays, Or, in the same way that solid-state electrons induced by electromagnetic waves are emitted from the surface of a semiconductor, exoelectrons are optical.

Occurs when a solid surface is stimulated mechanically, thermally, or chemically.

The generation mechanism is the same as in the case of photoelectron emission when light stimulation is used.

Exoelectron emission occurs even when the energy value of the stimulating light is less than the work function required for photoelectron emission of the material, and when the same energy of stimulating light is irradiated so that the light energy and the energy of the work function are equal, the amount of exoelectron emission is It has the property of being enhanced compared to normal photoelectron emission.

This characteristic is not unique to the material that makes up the surface, but is caused by surface conditions such as physical destruction of the surface, gas adsorption, or oxidation.

In this embodiment, changes in the state of the surface are observed by measuring the current value of exoelectrons, which is the amount of exoelectron radiation.

In FIG. 1, a semiconductor substrate 11 and its holder 10 are shown located outside in a chemical tank 1, and the semiconductor substrate 11 and its holder 10 are also shown being cleaned in a chemical solution in a chemical tank 2, and the semiconductor substrate 11 and its holder 10 are shown in a chemical solution at the top of a chemical tank 4. This shows how the degree of cleanliness is being observed.
This is a mechanism that allows for similar cleaning and cleaning degree measurements in various types.

After cleaning in each chemical tank is completed, the degree of cleaning of each semiconductor substrate 11 is measured by a detector 12. Electronic counting device 13
．． It is measured using the ammeter 14, and if a certain degree of cleaning cannot be obtained, it is determined and operated based on the electric signal that the cleaning process should be repeated again.

FIG. 2 shows the actual measurement results of the cleanliness and amount of exoelectrons using the mechanism of the present invention. Here, a silicon substrate 11 is used as the semiconductor substrate, and the results are shown after various cleaning processes. The silicon substrate 11 before cleaning is usually placed in various atmospheres or mechanically removed from the surface to evaluate its surface characteristics, and the amount of exoelectrons is 10-
The current is minute, less than A. The point where the silicon substrate 11 is set in the cleaning device is treated as before the cleaning process.

In this example, acetone, trichlorethylene, hydrofluoric acid, nitric acid, and pure water are used as cleaning chemicals.As the amount of exoelectrons increases, the degree of cleaning increases and the desired cleaning effect is achieved. This shows that it is observed electrically. In this example, specific cleaning values indicating cleaning standards are not shown, but the results are the results of an example in which the cleaning was performed as an example of a normal semiconductor processing cleaning process, and the cleaning was performed in the order of tanks 1 to 8 in Figure 1. .

This method of observing exoelectrons will be described in more detail.

FIG. 3 shows a method of exoelectron observation. Ultraviolet rays 20 as a substrate stimulation light source are irradiated onto a silicon substrate 21, exoelectrons 22 are generated, and a detector 23 and an electronic counting device 24 are generated.
The exoelectrons 22 are observed.

A thin oxide film 25 is formed on the surface of the silicon substrate 21 here.

Further, a circuit diagram of the exoelectron detector 23 is shown in FIG.

Exoelectrons 22 generated from the silicon substrate 21 are collected on an anode 26 to which a bias voltage is applied, and observed by an electron counting device 24 connected thereto.

The light source 20 for substrate stimulation is built into the rear part of the anode 26, and is a low-pressure mercury-filled light source (approximately 4
In W), the anode 26 is composed of a disk electrode with an opening in the center. An electrode with a diameter of 10 cylinders and an opening of 2Mφ was used, and the bias potential applied to this electrode was approximately 450 V/cm, with the distance between the substrate surface and the electrode being 2 cm.
It consists of a device that creates an electric field of cm. This exoelectron detector 23 measures in the atmosphere.

FIG. 4 shows the observation results of exoelectrons when the substrate is silicon and silicon oxide film and aluminum and aluminum oxide film.

Here, the state where the current value of exoelectrons is large is when the oxide film is thin.

In the case of a silicon substrate, when the silicon surface is in a clean state, that is, when it is covered with a thin oxide film, the exoelectron current value obtains a value of 10-"-10-9 A, which indicates the degree of cleanliness. It serves as a guideline.

When there are no contaminants on the surface, the exoelectron current value increases. That is, when foreign matter adheres to the solid surface due to contamination, the number of regular exoelectrons decreases.

This is because the amount of light incident on the surface decreases, and the amount of emitted exoelectrons decreases accordingly. Furthermore, the generation of emitted exoelectrons is suppressed by foreign matter on the surface, so even a small amount of foreign matter can cause a large change in the amount of exoelectrons.

Qualitatively, the amount of exoelectrons I can be determined as an electric signal from the following equation.

1=A−N where N is the surface cleanliness and A is the exoelectron emission coefficient.

Evaluating the results shown in Figure 2 from the above experiments, the amount of exoelectrons from the surface of the silicon substrate 11 before normal cleaning is 10-
In the range of eye A, change this from 1x1O-IO to 1.2X10
- The degree of cleanliness of the base was observed during the course of the change to A.

When we measured foreign substances using photoelectron spectroscopy on the silicon substrate 11 that had been cleaned in this example and the silicon substrate that had not undergone any treatment, there was no difference at all, and the foreign substances on the surface of the silicon substrate 11 were gone, and they were detected. The measurements were found to be reliable.

FIG. 5 shows the relationship between the amount of exoelectrons measured in this example and the degree of cleanliness of the substrate surface.

Effects of the Invention According to the present invention, the degree of cleanliness of a semiconductor substrate at several levels can be measured regardless of changes in the external environment.In other words, the measuring device is set in the atmosphere, and only the measuring section is always placed in the semiconductor substrate cleaning solution. You can keep it. Additionally, if the level of cleaning is insufficient at any stage, the board can be cleaned without exposing it to the outside air until the degree of cleaning is good, and the cleaning process can be done only once, eliminating the hassle of cleaning multiple times. This will lead to improved throughput. Furthermore, by using exoelectrons to measure the degree of semiconductor cleanliness, the degree of cleanliness can be precisely controlled, preventing a decrease in the yield of device formation due to residue on the substrate, and improving the yield.

By using this cleanliness measuring device, the cleaning process can be completely automated, and a stable automatic processing process can be constructed in a consistent semiconductor manufacturing process.

[Brief explanation of the drawing]

Figure 1 is a cleaning process diagram for explaining the present invention in detail, Figure 2 is a diagram showing the relationship between the cleaning progress and the amount of exoelectrons that occurred in an example of the present invention, and Figure 3 is a diagram of the amount of exoelectrons. Figure 4 is a diagram explaining the measurement principle, Figure 4 is a diagram showing the relationship between the film thickness of a metal oxide film and a semiconductor oxide film, and the amount of exo electrons, and Figure 5 is a diagram showing the relationship between the surface substrate cleaning degree and the amount of exo electrons in an example of the present invention. FIG. 3 is a diagram showing the relationship between quantities. 1 to 8... Chemical tank, 9... Chemical solution,
10... Semiconductor substrate holder 11...
・Semiconductor substrate, 12...Detector, 13...
...Electronic counting device, 14...Ammeter. Name of agent: Patent attorney Shigetaka Awano (1 person, 3 figures, 2 figures, 5 letters, 4 orders) Fig. 4 Z2... Δ calculation device 26...anode 26a, ant-μ' mouth sound φ

Claims (3)

[Claims] (1) A cleaning device characterized by having at least one exoelectron detector installed at a predetermined position within the cleaning device. (2) A first step of inserting an exoelectron detector installed in a non-contact with the semiconductor substrate into the cleaning device, a second step of cleaning the semiconductor substrate, and a step in which the amount of exoelectrons reaches a predetermined amount. A method for measuring the degree of cleanliness, comprising a third step of taking the product out of the cleaning device at a certain point. (3) A plurality of cleaning devices that carry out the processing consisting of the first, second, and third steps are arranged side by side, and the degree of cleaning is measured in parallel. How to measure the degree of cleanliness.