JP2973598B2 - Method and apparatus for detecting foreign matter on wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for counting foreign matter adhering on a wafer surface.

[0002]

2. Description of the Related Art In recent years, progress in semiconductor technology has been remarkable.
Ultra LSIs with a process rule of 0.5 μm or less are being developed. In such a situation, the influence on the yield of foreign particles and particles in the manufacturing process is becoming extremely large. In addition to making the production site an ultra-clean and clean environment, it is necessary to constantly monitor the actual amount of foreign matter on the wafer surface and take measures if there is a problem.

The present invention relates to such a technique for counting foreign matter on a wafer surface. An example of a conventional foreign matter counting technique on a wafer surface will be described below with reference to the drawings.

FIG. 4 shows the principle of a conventional foreign matter detection device. In FIG. 4, reference numeral 1 denotes a wafer to be measured. Reference numeral 2 denotes a rotary stage which scans the entire surface of the wafer 1 in combination with the linear moving mechanism 3. The laser light emitted from the He-Ne laser 4 is expanded by a beam expander 5 and is irradiated on the wafer 1 by a condenser lens system 7 via a mirror 6. The scattered light from the foreign material on the surface of the wafer 1 is received by a plurality of light receiving optical fibers 8 (usually only one is shown in FIG. 4) disposed around the optical axis of the laser, and the light is multiplied by a photomultiplier tube. The size and the number of foreign particles are calculated from the intensity of the scattered light and the number of pulses.

[0005]

However, in the above configuration, the size of foreign particles can be measured only up to a diameter of at least about 0.3 μm due to the laser light focusing limit. Further shorten the wavelength of laser light (Ar, He-Cd
It is considered that the limit value can be reduced to a diameter of about 0.1 μm by using a laser), but it is considered to be more difficult than that. On the other hand, in the LSI manufacturing process, it is necessary to control foreign particles less than 1/5 of the process rule.
There has been a demand for a technique capable of measuring foreign particles of about 05 μm.

The present invention has been made in view of the above problems, and provides a method for detecting ultra-fine particles of about 0.05 μm on a wafer surface.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an apparatus for detecting foreign matter on a wafer according to the present invention comprises a condenser capable of exposing a wafer to be measured to a supersaturated vapor pressure to cause a condensation reaction with foreign matter as a nucleus. It has a room.

[0008]

According to the present invention, a wafer to be measured is exposed to a supersaturated vapor pressure state of alcohol or the like in a condensation chamber by the above-described structure.
A condensation reaction is caused using foreign matter as nuclei, and the number of expanded condensation nuclei is measured. 0.05μm due to condensation reaction
A foreign substance having a diameter is enlarged to a diameter of 0.5 μm or more, so that the number of foreign substances can be easily measured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for detecting foreign matter on a wafer according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system configuration of an apparatus for detecting foreign matter on a wafer according to an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a wafer loader, 11 denotes a gate valve, 12 denotes a condensing chamber for generating a condensing reaction using foreign substances as nuclei, 13 denotes a foreign substance counting chamber for counting foreign substances enlarged by condensation, and 14 denotes a wafer unloader. .

FIG. 2 shows the configuration of the condensation chamber 12 in the embodiment of the present invention. In FIG. 2, 21
Denotes a temperature-controlled stage on which the wafer 1 is mounted, 22
Is a flow controller for controlling the amount of alcohol injected into the condensation chamber 12 to create a saturated vapor pressure state.

The operation of the apparatus for detecting foreign matter on a wafer configured as described above will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 1, a wafer 1 is loaded on a loader 10.
Through the gate valve 11 to the condensation chamber 12. In the condensation chamber 12, the wafer 1 is cooled to a predetermined temperature by a temperature-controlled stage 21 as shown in FIG. In this case, it is cooled to about 10 ° C. Next, the alcohol in the alcohol bottle 23 is injected from the flow rate controller 22 so as to have a substantially saturated vapor pressure. In this case, n-butyl alcohol was used, but other alcohols such as isobutyl alcohol can be used. Since the temperature of the wafer 1 is set to be several degrees to several tens degrees lower than the side wall of the condensation chamber 12, the alcohol vapor near the wafer surface is cooled and becomes supersaturated. When foreign matter is present on the wafer surface, it becomes a nucleus and alcohol condenses. The foreign matter in which alcohol condenses has a size of about 0.5 μm to several μm.

When the condensation reaction is completed, the wafer 1 is transferred to the foreign substance counting chamber 13. Here, foreign particles on the wafer 1 are counted by a well-known counting method as described in the conventional example. At this time, the temperature of the wafer stage (not shown) of the foreign matter counting chamber is set to substantially the same temperature as that of the condensation chamber. It is also desirable to introduce an alcohol that does not reach a saturated vapor pressure so that the condensed alcohol is less likely to sublime. The foreign matter enlarged by the condensation of the alcohol is counted, and data such as a map on the wafer and a particle size distribution are output. When the counting of the entire surface of the wafer is completed, the wafer 1 is transferred to the unloader 14 and taken out. Since the particle size is enlarged by condensation, the particle size distribution cannot be obtained accurately, but it is sufficient for the process control to find out the number of particles above a certain value, which is sufficient data for this purpose. .

If the temperature of the installation environment of the present foreign matter detection device is low, and if the side wall of the condensation chamber 12 cannot be made sufficiently lower than the wafer, a heater or the like is installed on the side wall of the condensation chamber 12.
It is also possible to raise the temperature.

As described above, according to the foreign matter detection apparatus of the present invention, even a fine foreign matter having a size of 0.05 μm or less can be enlarged and condensed easily by condensation. This is a very useful tool.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. (FIG. 3) is a schematic view of the condensation chamber 12 of the foreign matter detection device according to the second embodiment of the present invention. The present embodiment is different from the first embodiment in that a system in which the inside of the condensation chamber 12 can be weakly vacuumed by a pump 24 is different from that of the first embodiment. The wafer 1 is cooled to a predetermined temperature by the temperature-controlled stage 21 in the condensation chamber 12. Next, alcohol is injected from the flow rate controller 22 so as to have a substantially saturated vapor pressure. On this occasion,
By keeping the vacuum low, the alcohol is easily cooled by adiabatic expansion, so that the alcohol tends to have a supersaturated vapor pressure. By setting the temperature of the wafer 1 to be several degrees to several tens degrees lower than that of the side wall of the condensation chamber 12, the alcohol vapor near the wafer surface is cooled and becomes supersaturated. In addition to the condensing chamber 12, the foreign matter counting chamber 1
By making 3 a weak vacuum, the influence of conditions such as humidity outside the device is reduced, and it is also useful to reduce the scattering of laser light by gas molecules during counting.
It also has the effect of increasing the ratio and reproducibility.

In the embodiment, the case where the alcohol is condensed in the condensing chamber is shown. However, it is not always necessary to condense the alcohol. The result of the conventional method can be obtained by simply passing the condensing chamber and measuring the number of particles. It goes without saying that you can get

Table 1 shows a comparison of the effects of the present invention with the conventional example.

[0020]

[Table 1]

In the embodiment, the case where n-butyl alcohol is used is shown. However, other alcohols such as isobutyl alcohol and chemicals having the same function may be used.

[0022]

As described above, according to the present invention, a wafer to be measured is exposed to a supersaturated vapor pressure state such as alcohol in a condensation chamber to cause a condensation reaction with foreign matter as nuclei, and the number of expanded condensation nuclei is measured. Thus, even a fine foreign substance having a size of 0.05 μm or less can be enlarged by condensation and can be easily counted. As a result, it is possible to obtain extremely useful data for foreign substance management and yield improvement in the LSI manufacturing process.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a foreign object detection device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a condensation chamber for explaining an operation in the embodiment.

FIG. 3 is an explanatory diagram of a condensation chamber in a foreign object detection device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a conventional foreign matter detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 10 Loader 11 Gate valve 12 Condensation chamber 13 Foreign substance counting chamber 14 Unloader 21 Temperature control stage 22 Flow controller 24 Pump

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/66

Claims (6)

(57) [Claims] 1. An atmosphere containing foreign matter on a wafer surface as a nucleus.
After producing a large-diameter condensation product on the wafer surface by the gas condensation action, by observing the condensation product,
Wafer on foreign substance detecting method characterized by counting the foreign material on the wafer. 2. Exposing the wafer surface to a supersaturated vapor pressure of a gas.
And, the wafer on the foreign material detecting apparatus characterized by having a condensation chamber can with Turkey raw <br/> not hesitate to condensable of the gas foreign matter on the wafer as a nucleus. 3. A condensation chamber on wafer particle inspection detection device according to claim 2, further comprising a trial <br/> fee table whose temperature can be controlled in the wafer within. 4. The apparatus according to claim 2, further comprising a mechanism for holding the sample stage on which the wafer is mounted at the lowest temperature in the condensation chamber.
Inspection device for foreign matter on a wafer as described in the above. Wherein it comprises a mechanism for controlling the air pressure in the condensation chamber wafer on particle inspection detection device according to claim 2, wherein. 6. A mechanism for counting the number of foreign substances on a wafer is provided by a
Serial wafer on particle inspection detection device according to claim 2, characterized in that it is combined with the condensation chamber with a mechanism for transferring the wafer.