JPH0324768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for preventing surface contamination of a member to be treated.

Conventionally, in the manufacture of semiconductors such as VLSIs and LSIs, for example, when the surface of a semiconductor substrate is manufactured through numerous processing steps, when the substrate is transferred from one process to the next, during the transition Not only when the environment is in the atmosphere, but also in a vacuum processing room until the processing process is purified by vacuum exhaust, or in a clean room or clean booth until it is purified by circulating clean air. Even in this case, the clean surface of the pre-cleaned substrate may become contaminated during the process, resulting in a product of degraded quality or production loss.

The present invention provides a method for preventing contamination of the surface of a substrate during such transfer. Before transferring the substrate to a predetermined location, solid carbon dioxide, etc. It is characterized by forming a coating layer consisting of a film of a sublimable substance or an ice film of liquid such as water.

Furthermore, the present invention provides a surface contamination prevention device for carrying out the above method, and includes a clean environment generating device consisting of a vacuum device or a clean air generator for creating a clean environment in a space that accommodates a substrate; and a coating layer forming device for forming a coating layer consisting of a sublimable substance film such as solid carbonic acid or a liquid ice film such as water on the clean surface of the substrate.

Next, an embodiment of the present invention will be described using as an example a case in which a substrate whose surface has been cleaned is transferred to the next photoresist coating step in a semiconductor manufacturing process such as an N-channel MOS process.

In Fig. 1, reference numeral 1 indicates a silicon substrate having _two SiO layers on the surface, and the substrate 1 is kept in a space such as a vacuum container, a clean room, or a clean booth, and is not exposed to vacuum exhaust or clean air. The generator generates clean air within a clean environment. This is transferred to the next photoresist film forming step, but before that, the clean surface 1a of the substrate 1 is
For example, a coating layer is formed as follows. That is, the outlet pipe 2 from a clean liquid nitrogen cylinder (not shown)
A nozzle 3 at the tip of is provided in the space, and the nozzle 3
More vaporized low-temperature N ₂ gas is blown onto the substrate 1 to cool the temperature of the substrate 1 to −80° C. or lower. Next, clean _CO2 gas from a _CO2 gas cylinder (not shown) is applied to the clean surface 1a of the cooled substrate 1.
When the CO ₂ gas is sprayed uniformly over the entire surface from the CO 2 jet nozzle 4, the CO ₂ gas is condensed and a coating layer 5 made of snow-like CO ₂ particles is formed on the surface of the CO 2 gas as fine CO ₂ particles. Its thickness is usually 0.1 μm or more. Needless to say, the thickness is determined depending on the expected level of contamination. After forming the coating layer 5 on the substrate 1 using the coating layer forming apparatus consisting of a cooling N ₂ gas nozzle and a CO ₂ gas nozzle, the photoresist coating is then placed in the required vacuum chamber or clean room. Move on to the forming process. In such a case, even if the substrate 1 is moved in the air or in an atmosphere with insufficient cleanliness, the substrate 1 is covered with the coating layer 5, so foreign substances such as fine dust will be removed from the coating layer. 5, the clean surface 1a of the substrate 1 is isolated from contamination by the coating layer 5 and is not contaminated. After the transfer, the substrate 1 placed in a clean environment is subjected to a coating layer removal device installed on the spot, such as a hot air gas jetting nozzle 6, as shown in the second figure, before forming a photoresist film thereon. When warmer air is blown onto the CO ₂ particle coating layer 5, the particles immediately sublimate and disappear, revealing a clean surface 1a. Instead of hot air, suitable heating means such as sub-irradiation heating may be used.
When this photoresist coating is formed in a clean container with the required degree of vacuum, the vacuum pump acts as a coating layer removal device to evacuate the interior of the container and suck and sublimate and exhaust the CO ₂ particle coating layer 5. You can force it. By this warm air and vacuum evacuation, not only the CO ₂ particle coating layer 5 is removed, but also the foreign matter attached to the coating layer 5 is removed by the hot air or vacuum suction, and the substrate is removed. 1 surface 1
Since the surface 1a is kept clean without remaining on the surface 1a, it is possible to form a photoresist film thereon and perform a surface treatment that does not contain any dirt at all. Incidentally, if the warm air nozzle 6 is installed horizontally along the surface of the substrate 1 as shown in the figure, and the jet stream is caused to flow along the surface from the side, foreign matter can be effectively removed.

The flow velocity of the jet is appropriately set.

The method for forming the coating layer 5 of CO ₂ particles is as follows:
This can be done more easily as shown in the third diagram. That is, without pre-cooling the substrate 1 with N ₂ gas as described above, a high-pressure liquefied carbon dioxide cylinder 7 is prepared, and a nozzle 9 at the tip of a discharge pipe 8 to be discharged from the cylinder 7 is prepared.
More liquefied carbon dioxide is ejected and its adiabatic expansion produces CO ₂
Particles are generated and transferred to the clean surface 1 of the substrate 1.
a to form a CO ₂ particle coating layer 5 of a required thickness. With this method, the coating layer 5 can be easily formed on a relatively large area of the substrate surface.

As mentioned above, for forming the coating layer 5, a sublimable substance such as CO 2 which is inert to the substrate 1 and easily sublimes is typically preferable, but in some cases, a sublimable substance such as CO ₂ is preferably used. It may be a liquid such as water that freezes easily and evaporates easily and does not contaminate the substrate. An example of its implementation is shown in FIG. For example, similar to the apparatus shown in FIG. 1, low temperature gas such as _N2 gas is ejected from a nozzle 10 for blowing out low temperature gas at a temperature below 0°C, and after spraying the substrate 1 to a temperature below 0°C, a spray device 11 is applied to the substrate 1. Pure water is uniformly sprayed onto the clean surface 1a of the substrate 1 to form an ice film coating layer 5 in which water condenses to a desired thickness.
form. When this ice film coating layer 5 is formed, its removal in the photoresist process etc.
It is preferable to introduce the substrate 1 into a low-temperature vacuum drying container or room at a temperature of 0° C. or lower and remove the ice film by sublimation and suction without melting and vaporizing. This prevents foreign matter adhering to the coating layer from remaining on the substrate surface.

In addition, whether it is the CO ₂ particle coating layer or the ice film coating layer, if necessary, during the transfer of the substrate 1, a certain process, for example, may be carried out to prevent CO ₂ from sublimating or ice from melting. A channel-shaped or pipe-shaped passage is provided to connect the conveyor to the next process, and CO ₂ is removed from the inside of this conveyor passage.
In the case of particles, keep them at about -70℃ or below to prevent sublimation.
In the case of an ice film of water, it is possible to keep it in an atmosphere cooled to below 0°C to prevent the frozen coating layer 5 from chipping and contamination during transportation. Use a cold container with the box and surrounding area cooled with liquid nitrogen, etc.

It goes without saying that the coating process for a plurality of substrates may be performed at one time.

According to the present invention, when a substrate with a clean surface is transported, a coating layer consisting of a sublimable substance film such as solid carbonic acid or a liquid ice film such as water is applied to the surface in a clean environment. Since the material is transported after being formed, the clean surface can be transferred to the next processing step without being contaminated during the transfer.
A surface-treated product of good quality can be obtained, and when the coating layer is made of solid carbonic acid, the coating layer can be removed very easily, which is advantageous.

[Brief explanation of the drawing]

FIG. 1 is a side view of one example of implementing the present invention, FIG. 2 is a side view of one example when the coating layer is removed, FIG. 3 is a side view of another example, and FIG. 4 is a side view of yet another example. show. DESCRIPTION OF SYMBOLS 1...Substrate, 1a...Clean surface, 3, 10... Cooling nozzle, 4, 9, 11... Film-forming substance ejection nozzle.

Claims (1)

[Scope of Claims] 1. Before transferring a substrate to a predetermined location, a coating consisting of a sublimable substance film such as solid carbonic acid or a liquid ice film such as water is applied to the clean surface of the substrate in a clean environment. A surface contamination prevention method characterized by forming a layer. 2. A clean environment generating device consisting of a vacuum device or a clean air generator to create a clean environment in the space that accommodates the substrate, and a clean environment generating device consisting of a vacuum device or a clean air generator to create a clean environment in the space that accommodates the substrate, and a sublimable substance film such as solid carbonic acid or a liquid such as water on the clean surface of the substrate. A surface contamination prevention device comprising a coating layer forming device for forming a coating layer consisting of an ice film. 3. A patent claim in which the coating layer forming device comprises a cooling device for cooling the substrate and a spraying device for spraying a film-forming substance made of a sublimable substance such as carbon dioxide gas or a liquid such as water onto the cooled substrate. The surface contamination prevention device according to item 2. 4. The surface contamination prevention device according to claim 2, wherein the coating layer forming device comprises a spraying device that sprays solid particles of a sublimable substance such as solid carbonic acid onto the substrate. 5 After forming a coating layer consisting of a sublimable substance film such as solid carbonic acid or a liquid ice film such as water in a clean environment on the clean surface of the substrate, this is subjected to the following surface treatment in a clean environment. Transfer to the process and remove the coating layer without melting it using a coating layer removal device consisting of vacuum exhaust or hot air, etc., and remove contaminants that adhered to the coating layer during transfer without leaving them on the clean surface of the substrate. A surface contamination prevention method characterized by: 6. Provide cooling passages or cooling containers to prevent sublimation or melting of the frozen coating layer during transfer of substrates equipped with a frozen coating layer consisting of a sublimable substance film such as solid carbon dioxide or a liquid ice film such as water. A surface contamination prevention method characterized by preventing contamination of a substrate during transfer due to loss of the frozen coating layer therein.