JPH0382123A - Drying process and device therefor - Google Patents

Abstract

PURPOSE:To clean up any water drips sticked on a wafer surface instantaneously and throughly by a method wherein an element to be dried up is arranged in high temperature inert gas atmosphere irradiated with infrared rays so as to be dried up. CONSTITUTION:A gas feeder pipe 4 heated by emission heat from a medium wavelength infrared ray lamps 5 is led to the upper part in a drying chamber 1 and then bent downward in the drying chamber 1. Successively, short wavelength infrared ray lamps 6 are lighted with the medium wave-length infrared ray lamps 5 lighted as they are and then a carrier arm 7 fitted with a wafer 8 whose surface is turned to the short wavelength infrared ray lamps 6 side is inserted into the drying chamber 1 to be rested on a specific position. The surface of the wafer 8 is rapidly heated by the infrared rays emitted from the medium wavelength and short wavelength infrared ray lamps 5 and 6 to evaporate the water content sticked on the surface of the wafer 8. After the wafer 8 is rested in the drying chamber 1 for specific time, the carrier arm 7 is pulled out of the drying chamber 1 to replace the wafer 8 with the other wafer 8 and then inserted into the drying chamber 1 again to dry up the other wafer 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a technology for drying articles, and in particular, to a technology that is effective when used for drying objects to be dried that have water droplets or the like attached to them after washing or the like. .

[Conventional technology]

For example, in the manufacturing process of semiconductor wafers (hereinafter simply referred to as wafers), when performing etching, there is dry etching in which aluminum alloy (Al-Cu-5i) is etched with chlorine gas, but this method etches the wafer surface. Aluminum wiring corrodes due to residual chlorine.Therefore, after etching is complete, wet cleaning is performed to remove residual chlorine as an anti-corrosion treatment.After this wet cleaning, centrifugal drying or IPA (isopropyl alcohol) The drying process is performed using a steam drying method.

In addition to dry etching, there is also an etching method in which a pattern is formed by wet etching the oxide film on the wafer surface, and in this case as well, a drying process such as an IPA vapor drying method is performed as a post-process.

Such a drying technique using IPA vapor is, for example, as described in Japanese Patent Application Laid-Open No. 56-168072, in which a processing liquid made of an organic solvent such as IPA is stored at the bottom of a processing tank, heated to turn it into vapor, Wafers, which are objects to be dried, are being dried.

By the way, the present inventor investigated stain contamination caused by the IPA steam drying method.

The following are the techniques studied by the present inventor, and the outline thereof is as follows.

In other words, in the IPA vapor drying method, organic solvent vapor is supplied from below the object to be dried, and water droplets adhering to the wafer surface are converted into organic solvent droplets that are condensed on the wafer surface. The wafer surface is dried by dissolving (or dispersing) and removing the wafer. Note that as the size of the wafer increases, a larger processing tank is required.

[Problem to be solved by the invention]

However, in the IPA steam drying method as described above,
As the size of wafers increases, so does the processing tank itself, making it difficult to secure the necessary amount of steam, resulting in stain-like stains called watermarks on the wafer surface.

In addition, sodium (Na) and potassium (K) are present in IPA.
If it contains impurities such as or contains moisture,
This causes ionic contamination on the wafer surface and stain contamination due to insufficient drying. The occurrence of such stains leads to defective characteristics of highly integrated circuit elements.

Regarding watermarks, see IEICE Report SDM87-188, March 15, 1988, P3.
There is a description on pages 3 to 38. Briefly, an oxidation reaction occurs at the interface between the wafer surface and the water droplets attached to the surface, due to oxygen dissolved in the water droplets from the atmosphere.
The generated silicon (Si) oxide is hydrated and dissolved in water droplets, and the watermark is what is precipitated as the water droplets evaporate.

In order to prevent the formation of this water mark, it is possible to increase the capacity of the processing tank using a heat source such as a heater to obtain the required amount of steam, but IPA, which is the processing liquid, is flammable and safety must be ensured. There are difficulties in

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a technology capable of instantaneously and highly cleaning water droplets adhering to a wafer surface without using an organic solvent.

The above objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the material to be dried is placed in a high-temperature inert gas atmosphere that is irradiated with infrared rays to perform drying.

[Effect]

According to the above-described means, the high-temperature inert gas heats the material to be dried and prevents the oxidation reaction at the interface between the water droplets attached to the surface and the material to be dried, and the infrared rays provided at the same time heat the material to be dried. absorbed into the air and instantly dispersed or evaporated. Therefore, the drying process can be completed safely and stably in a short time without using an organic solvent.

〔Example〕

FIG. 1 is a front sectional view showing an embodiment of a drying apparatus according to the present invention.

A vertically long drying chamber 1 is formed in the center, an inert gas supply port is formed in the upper part, and an outlet for wafers, which are objects to be dried, is formed in the lower part. A heating chamber 2 is formed on one side of the drying chamber 1, and a heating chamber 3 is formed on the opposite side with the drying chamber 1 in between. A quartz glass plate or the like that easily transmits infrared rays is disposed on the surface of each heating chamber 2.3 that is in contact with the drying chamber 1.

A gas supply pipe 4 for supplying an inert gas into the drying chamber 1 is arranged in a meandering manner within the heating chamber 2 . The gas supply pipe 4 is configured to be irradiated with a portion of infrared rays from a medium wavelength infrared lamp 5 as a heat source.

Furthermore, inside the heating chamber 2, adjacent to the gas supply pipe 4 and closer to the drying chamber 1, a plurality of medium wavelength infrared lamps 5 are vertically arranged at regular intervals.

On the other hand, inside the heating chamber 3, a plurality of short wavelength infrared lamps 6 are vertically arranged at regular intervals.

The mid-wavelength infrared lamp 5 has a characteristic of emitting infrared rays with a wavelength of around 2.5 μm (hereinafter referred to as mid-wavelength infrared rays).
The short wavelength infrared lamp 6 emits infrared light with a wavelength of around 1.2 μm (
It has the characteristic of emitting short-wavelength infrared radiation (hereinafter referred to as short-wavelength infrared rays).

A transport arm 7 is disposed in the drying chamber 1 so as to be freely inserted into and withdrawn from the inside and outside of the room, and a wafer 8, which is an object to be dried, is attached to the tip of the arm 7.

In the above configuration, in order to dry the wafer 8, first, the medium wavelength infrared lamp 5 is turned on, and then nitrogen gas as an inert gas is introduced into the gas supply pipe 4. The gas supply pipe 4 is heated (for example, 400° C.) by the heat emitted from the medium-wavelength infrared lamp 5, is fed into the upper part of the drying chamber 1, and flows down inside the drying chamber 1.

Next, the short wavelength infrared lamp 6 is turned on while the medium wavelength infrared lamp 5 is turned on, and the transfer arm 7 with the wafer 8 attached is inserted into the drying chamber 1 with the surface of the wafer 8 facing the short wavelength infrared lamp 6 side. and hold it in place. The surface of the wafer 8 is rapidly heated by the infrared rays from the medium wavelength infrared lamp 5 and the short wavelength infrared lamp 6, and the moisture attached to the surface of the wafer 8 is evaporated.

After the wafer 8 remains in the drying chamber 1 for a certain period of time, the transfer arm 7
out of the drying chamber 1, remove the wafer 8 from the transfer arm 7, replace it with another wafer 8, and insert it into the drying chamber 1.
A drying process is performed as described above.

According to the above embodiment, the wafer 8 in the drying chamber 1 is heated by preheated nitrogen gas, the medium wavelength infrared lamp 5, and the short wavelength infrared lamp 6, respectively. At this time, since the emission wavelength of the short wavelength infrared lamp 6 disposed opposite to the back surface of the wafer 8 is as short as 1.2 μml; Only raise the temperature.

FIG. 2 shows the temperature rise characteristics when a silicon wafer is heated with an infrared lamp.

In the figure, characteristic a is when the wafer 8 is irradiated with infrared rays by a short wavelength infrared lamp 6, and characteristic a is when the wafer 8 is irradiated with infrared rays by a middle wavelength infrared lamp 5. According to the results of a drying process performed by the present inventors for 4 minutes, irradiation with the short wavelength infrared lamp 6 was able to increase the wafer surface temperature by about twice as much as the medium wavelength infrared lamp 5. Furthermore, it has been confirmed that by shortening the distance between the wafer 8 and the short wavelength infrared lamp 6, the surface temperature of the wafer 8 can be further increased in a short time.

On the other hand, the water droplets attached to the surface of the wafer 8 are heated by nitrogen gas, heat transfer from the wafer 8, infrared irradiation to the surface by the short wavelength infrared lamp 6, and medium wavelength infrared lamp 5, and the wafer Water molecules absorb the mid-wavelength infrared rays that have passed through the back surface of 8, resulting in effective evaporation.

FIG. 3 shows the temperature rise characteristics when the silicon wafer is heated by an infrared lamp by changing the heating method. That is, characteristic C indicates the wafer temperature characteristic under a nitrogen gas atmosphere heated to 300° C., and characteristic d indicates the wafer temperature characteristic when the wafer warms when the wafer is irradiated with the short wavelength infrared lamp 6 and the medium wavelength infrared lamp 5 is irradiated. ing.

By irradiating the short wavelength infrared lamp 6 in a nitrogen gas atmosphere at 300° C., the temperature difference between the wafer 8 and the water droplets can be instantly increased, and most of the water droplets can be scattered and removed from the surface of the wafer 8. . Furthermore, moisture remaining on the surface of the wafer 8, such as at the step portion, is also evaporated in a short time by medium wavelength infrared rays.

FIG. 4 shows the temperature rise characteristics during the drying process of the wafer 8 having a pattern formed on its surface.

In the figure, the characteristic f is the wafer temperature characteristic when infrared rays are irradiated by the short wavelength infrared lamp 6, and the characteristic g is the wafer temperature characteristic when the short wavelength infrared lamp 6 is irradiated from the front side of the wafer 8 under a nitrogen gas atmosphere at 400°C. The graph shows the wafer temperature characteristics with respect to processing time when irradiated with a medium wavelength infrared lamp 5.

Even if the wafer is patterned, by irradiating it with infrared rays in a high-temperature nitrogen gas atmosphere, the time for the surface temperature of the wafer 8 to reach a constant value of 100°C due to latent heat due to evaporation of moisture can be shortened. , moisture on the surface of the wafer 8 can be completely evaporated in a short time. As a result, defective drying of the wafer 8 can be prevented and uniform and highly clean drying can be performed.

Since the drying chamber 1 has an opening at the bottom, there is a concern that the wafer 8 may come in contact with air during drying and oxidize. However, by inserting the transfer arm 7 sufficiently deep into the drying chamber 1 , it is possible to suppress the oxidation reaction at the interface between the surface of the wafer 8 and the water droplets during drying.

Above, the invention made by the present inventor has been specifically explained based on Examples, but it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. stomach.

For example, although an example is shown in which nitrogen gas is used as the inert gas, other gases other than nitrogen gas, such as argon, may also be used. Further, although an example has been shown in which nitrogen gas is preheated to 400° C., this can be changed depending on the surface condition of the wafer 8.

Furthermore, the infrared lamp may be turned on all the time, or may be turned on immediately before inserting the wafer 8 into the drying chamber 1.

In the above description, the invention made by the present inventor was mainly applied to the application field of wafer drying, but the invention is not limited to this.
For example, it is applicable to magnetic disks made of aluminum, masks made of glass substrates, and the like.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical ones are as follows.

In other words, since the material to be dried is placed in a high-temperature inert gas atmosphere that is irradiated with infrared rays, drying is performed in a short period of time without oxidation reactions occurring and without creating water marks. It becomes possible to perform highly clean drying.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing an embodiment of the drying apparatus according to the present invention, Fig. 2 is a temperature rise characteristic diagram when a silicon wafer is heated with an infrared lamp, and Fig. 3 is a diagram showing temperature rise characteristics when a silicon wafer is heated with an infrared lamp. FIG. 4 is a temperature rise characteristic diagram when a silicon wafer is heated. FIG. 4 is a temperature rise characteristic diagram when a wafer 8 having a pattern formed on its surface is subjected to a drying process. DESCRIPTION OF SYMBOLS 1... Drying chamber, 2.3... Heating chamber, 4... Gas supply pipe, 5... Medium wavelength infrared lamp, 6... Short wavelength infrared lamp, 7... Transfer arm, 8 ...Wafer. 1st Figure 1: Drying chamber 7: Transfer arm 5 Medium wavelength infrared lamp 6 Short wavelength infrared lamp Figure 1/(distance between bar lamps) (crn-”) Elapsed time (minutes) 1 Rad 0 0 0 0 Processing Time (seconds) -Uto

Claims (1)

[Scope of Claims] 1. A drying method characterized by drying an object to be dried by placing it in a high-temperature inert gas atmosphere that is irradiated with infrared rays. 2. The infrared rays have a wavelength range that transmits heat to a surface layer of the object to be dried, and a wavelength range that transmits heat to at least a deep layer of the object to be dried. Drying method. 3. The drying method according to claim 1, wherein the object to be dried is a silicon semiconductor wafer. 4. The drying method according to claim 1, wherein the inert gas is nitrogen gas. 5. The wavelength range for transmitting heat to the surface layer is a wavelength of 1.2μ.
3. The drying method according to claim 2, wherein the drying method is in the vicinity of m. 6. The wavelength range that transmits heat to the deep layer is a wavelength of 2.5μ.
3. The drying method according to claim 2, wherein the drying method is in the vicinity of m. 7. A drying chamber formed to surround the inserted object to be dried; a conveyance means for carrying the object to be dried into and out of the drying chamber in a vertical direction; A drying apparatus comprising: an infrared generating means for irradiating the object to be dried with infrared rays; and a preheating means for preheating an inert gas supplied to the drying chamber. 8. The infrared ray generating means includes a first infrared lamp that concentrates infrared rays on the surface layer of the object to be dried, and a second infrared lamp that irradiates infrared rays with a longer wavelength than the infrared lamp from the opposite side of the first infrared lamp. 8. The drying apparatus according to claim 7, comprising: two infrared lamps.