JPH0695511B2 - Washing and drying treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to cleaning a surface of a thin substrate to be processed (hereinafter referred to as “wafer”) such as a semiconductor wafer or a glass substrate,
It relates to a method of draining and drying.

[Conventional technology]

Conventionally, for example, in Japanese Unexamined Patent Publication No. 59-100540 (the title of the invention: "Treatment method in a centrifugal dryer used for treating silicon wafers"), the required time (0 to 0 t ₁ ) Rotate at a constant speed,
Next, after stopping the water shower, rotate at high speed for the required time (t _{1 to} t ₂ ), and then blow nitrogen gas to the wafer surface at the high speed rotation for the required time (t _{2 to} t ₃ ) to finish the drying process. The method of treatment in the centrifugal dryer described above is known (5th
See figure).

[Problems to be solved by the invention]

In Japanese Patent Application Laid-Open No. 59-100540, an inert gas is supplied and dried assuming that the water droplets on the wafer surface have been shaken off by the high speed rotation after a required time (t ₂ −t ₁ ) from the start of the high speed rotation. However, the required time (t ₂ −t ₁ ) needs to be experimentally obtained and reset depending on the surface condition of the wafer, the material of the wafer, the dimensions of the wafer, and the like.

On the other hand, when irradiating the wafer surface with light instead of supplying an inert gas to dry the wafer, there is a problem that if water droplets remain on the wafer surface, that portion remains as a stain, It is necessary to completely dehydrate the surface of the wafer other than the fine recesses formed as a pattern and then dry it by irradiation with light. For this purpose, it is a problem to accurately detect the completion of the dehydration process.

[Means for solving problems]

According to the present invention, the cleaning liquid is supplied to the surface of the wafer while rotating the wafer to clean it, and then the wafer is rotated at a higher speed than during cleaning to shake off the cleaning liquid adhering to the wafer surface to deliquify the wafer. In the method of irradiating with light to heat and drying, during the liquid removal treatment, the peripheral surface of the wafer is irradiated with light, and reflected light or transmitted light is detected from the surface,
The cleaning / drying processing method is characterized in that when the signal level of the detection signal becomes substantially constant, it is determined that the liquid removal processing is completed, and then the drying processing is performed.

[Action]

In the liquid removal process, when the wafer surface is irradiated with light and the reflected light or transmitted light from the surface is detected, the detection signal before and after that is due to irregular reflection or absorption of light on the water drop surface on the wafer surface. Although it fluctuates greatly, in the latter stage of the liquid removal process, the thin water film remaining on the wafer surface causes interference in the reflected light or the transmitted light, and the detection signal changes to a signal with a certain amplitude and forms on the wafer surface. When the liquid removal process is completed in a state where the water content other than the fine recesses thus formed is shaken off by the centrifugal force, the detection signal becomes almost constant. In this case, when the wafer is rotated at a high speed in the liquid removal process, the cleaning liquid on the wafer surface moves from the central portion to the peripheral portion, and the liquid removal progresses from the central portion to the peripheral portion of the wafer. By irradiating a point on the peripheral surface of the wafer with light and detecting its reflected light or transmitted light, if the end of the liquid removal process is determined based on the detection signal, the wafer surface The deliquoring process has been completed in the entire range. Further, since the light irradiation on the wafer surface for the determination at the end of the liquid removal processing is performed largely on the peripheral portion of the wafer, there is no obstacle in supplying the cleaning liquid to the central portion of the wafer. Then, after the completion of the liquid removal processing is detected, the wafer surface is irradiated with light to be dried, so that the wafer can be uniformly and completely dried.

〔Example〕

FIG. 1 is a flow chart showing a method according to the present invention, and FIG. 2 is a schematic diagram showing an embodiment of an apparatus for carrying out the flow chart. An explanatory view showing the change is shown in FIG.

In the schematic diagram of FIG. 2, 1 is a chuck for holding the wafer W and rotating it horizontally, 2 is a nozzle for supplying a cleaning liquid above the chuck 1 and is suspended, and 3 and 4 are one end of the wafer W in the peripheral portion thereof. Is a light projecting fiber and a light receiving fiber suspended on the inner surface of the surface treatment chamber 5 so as to be close to each other. Further, a drain pipe 9 for discharging the processing liquid is provided on the bottom surface of the surface processing chamber 5, and a pressure reducing pipe 12 connected to a vacuum source (not shown) is arranged on the side wall of the processing chamber. There is. Further, the upper lid 5'of the processing chamber 5 is constructed of a transparent plate which can be opened and closed, and an infrared irradiation lamp 10 for drying the wafer and an ultraviolet irradiation lamp 11 which is turned on as necessary are arranged above the transparent lid. There is.

A light emitting means 7 such as a light emitting diode or a semiconductor laser is provided at the other end of the light projecting fiber 3, and a photoelectric conversion means 6 is provided at the other end of the light receiving fiber 4. The output signal from the photoelectric conversion means 6 is input to the control means 8, and the surface processing state of the wafer W can be detected by the signal from the photoelectric conversion means 6.

FIG. 6 is a block diagram showing an embodiment of the control means 8, and the output signal from the photoelectric conversion means 6 is first an amplifier.
The signal is converted into a digital signal by the A / D converter 82 via 81 and input to the central processing unit (CPU) 83. The CPU 83 performs a predetermined calculation process, for example, a differentiation process, and terminates the liquid removal process when the differentiated output signal from the photoelectric conversion means 6 becomes a predetermined level value or less for a certain period. Therefore, the rotation control circuit
The drive motor of the rotary chuck 1 is stopped via 84.

Hereinafter, description will be given according to the flowchart of FIG. First, when the process is started (step S ₀ ), the wafer W held by the chuck 1 starts to rotate horizontally. At this time, the rotation speed N changes from 0 to N ₁ as shown in FIG.
From FIG. 2, the cleaning liquid is supplied to the wafer W (step S ₁ ).

When the rotation speed of the wafer W is N _{1, the} time required for the surface of the wafer W (0
~ T ₁ ) After the cleaning process, the rotation speed N of the wafer W is N ₁ to N ₂
(N ₂ ≧ 2000 rpm), and the process moves to the liquid removal treatment step (step S ₂ ) in which the centrifugal force turns back. Simultaneously with the shift to the liquid removal processing step, light is emitted from the light emitting means 7 to the surface of the wafer W via the fiber 3 and the reflected light is made incident on the photoelectric conversion means 6 via the fiber 4, thereby making the wafer The change of the reflected light on the surface of W is represented by the electric signal V
Is input to the control means 8. FIG. 3B shows an example of the output signal V from the photoelectric conversion means 6, and while the water droplets of the cleaning liquid on the wafer surface remain, the irradiation light on the wafer surface is irregularly reflected, so that the light receiving fiber. Although the change in the amount of light entering 4 is large, the droplet is output when the water droplets of the cleaning liquid are completely shaken off from the surface of the wafer W other than the fine recesses on which the pattern is formed, and a thin water film remains on the surface. When the amplitude of the signal becomes constant and finally the water in the portion other than the concave portion disappears, the output signal V from the photoelectric conversion means 6 corresponding to the amount of received light becomes substantially constant. This output signal V
There is determined the after deliquor processing end time t ₂ becomes constant. For example, the rotation speed N ₂ in FIG. 3A is N ₂ = 500, 1000, ₂₀₀ , respectively.
At 0 and 4000 rpm, the time (t ₂ −t ₁ ) required for the dehydration treatment in FIG. 3B is 60, 40, 25 and 15 seconds, respectively. Further, the determination after the completion of the liquid removal process is
A predetermined time after the time t _{2 in} FIG. 3B can be determined as the end of the liquid removal process.

After the completion of the liquid removing process, the infrared irradiation lamp 10 irradiates the surface of the wafer W with infrared rays to dry the surface of the wafer (step S ₄ ). If the wafer W is made of silicon, the wavelength of 1.2 μm is the wavelength most easily absorbed by the silicon substrate.
It is preferable to use, as the infrared irradiation lamp 10, a halogen lamp mainly containing rays in the infrared region.

FIG. 4 shows a graph of the number of rotations of the wafer W for explaining another embodiment of the cleaning / drying processing method according to the present invention.
Here, it is disclosed that the control means 8 (FIG. 2) is also provided with a function of detecting the end point (end point) of the surface treatment such as etching treatment. The rotation is performed at a predetermined rotation speed N ₁ . An etching liquid is supplied to the surface of the wafer W from a nozzle (not shown in FIG. 2) to selectively etch the metal thin film on the surface of the wafer W, and the etching state of the thin metal film is checked through the optical fibers 3 and 4. The end point of the etching process is detected based on the change in the light reflected from the surface.

At the end of the etching process, t ₁ is set as the end point (EP), the supply of the etching liquid is stopped, and the wafer W
The number of rotations is changed from N ₁ to N ₂ , and a cleaning liquid is supplied to the surface of the wafer W to clean the surface of the wafer W. After the lapse of a predetermined time, the supply of the cleaning liquid is stopped, the rotation speed is switched from N ₂ to N ₄ , the cleaning liquid remaining on the surface of the wafer W is shaken off, and at the same time, the end point of the liquid removal processing is detected in the same manner as described above. . After that, when the amount of the reflected light of the wafer W incident on the fiber 4 becomes constant, t ₃ is defined as the end of the liquid removing process, and then the surface of the wafer W is irradiated with ultraviolet rays from the lamp 11 for a predetermined time t _4. , Decomposes organic and inorganic impurities adhering to the surface of the wafer W.

Next, the rotation speed of the wafer W is switched from N ₄ to N ₃ , pure water is supplied to the surface of the wafer W, and decomposed impurities on the surface of the wafer W are removed from the surface of the wafer W. It should be noted that it is preferable that the cleaning with pure water and the irradiation with ultraviolet rays are performed for a certain period of time in order to decompose and remove impurities.

Required time (t _{4 to} t ₅ ) After cleaning with pure water, IP on the wafer surface
Supply a solvent such as A. (iso-propyl-alcohol),
It replaces the water remaining on the wafer surface.

Further, when the solvent such as IPA is supplied to the surface of the wafer W, if the solvent is irradiated with ultraviolet rays at the same time as the supply, the solvent such as IPA is dissolved, so that the ultraviolet irradiation and the solvent supply are controlled so as not to overlap. .

Next, the number of rotations of the wafer W is switched from N ₃ to N ₄ , and the liquid removing process is started again (t _{6 to} t ₇ ), the end point of the liquid removing process is detected, and the liquid removing process is ended. After the completion of the liquid removal process, the number of rotations of the wafer W is N _{4 and} the drying process is started.
Thus, the surface of the wafer W is irradiated with infrared rays for a predetermined time (t _{7 to} t ₈ ).

It goes without saying that the liquid removal treatment step and the light irradiation drying step described above can be performed in a decompression chamber.

FIG. 7 is a schematic diagram showing another embodiment (in the case of transmitted light) of the method according to the present invention, in which light having a main wavelength of, for example, 1.2 μm is emitted from the light emitting means 7 to the silicon wafer W. By irradiating and receiving the transmitted light by the photoelectric conversion means 6 and inputting it to the control means 8, it is possible to detect the end of the liquid removal processing as in the case of the reflected light.

〔The invention's effect〕

After cleaning the wafer, rotate it at a high speed, and after removing the liquid by centrifugal force, when drying the wafer by light irradiation, do not rotate the wafer at an unnecessarily high speed, and conversely, the cleaning liquid remains on the wafer surface. The problem of irradiating the surface of the wafer with light to cause spots on the surface of the wafer is eliminated by accurately detecting the end point of the liquid removal process, and the minimum required liquid removal according to the number of wafer rotations is performed. It can be processed in processing time. Further, since the light irradiation on the wafer surface for the determination at the end of the liquid removal processing is performed at the peripheral portion of the wafer and at one point thereof, the configuration of the apparatus for carrying out the method according to the present invention becomes complicated. Nothing.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example for carrying out the method according to the present invention, FIG. 2 is a schematic view of an apparatus showing one example for carrying out the method according to the present invention, and FIG. FIG. 4 is an explanatory view showing an example for carrying out the method, FIG. 4 is an explanatory view showing another example for carrying out the method according to the present invention, FIG. 5 is a conventional explanatory view, and FIG. 6 is a control. FIG. 7 is a block diagram showing an example of the means, and FIG. 7 is a schematic view of an apparatus showing another example for carrying out the method according to the present invention. W ... Wafer, 1 ... Rotating chuck, 2 ... Nozzle, 3 ... Light emitting fiber, 4 ... Light receiving fiber, 5 ... Surface treatment chamber, 6 ... Photoelectric conversion element, 7 ... Light emitting means , 8 ... control means, 9 ... drainage pipe, 10 ... infrared lamp, 11 ... ultraviolet lamp, 12 ... decompression pipe.

Claims (1)

[Claims] 1. A substrate to be processed is rotated to supply a cleaning liquid to the surface thereof for cleaning, and thereafter, the substrate to be processed is rotated at a higher speed than during cleaning to shake off the cleaning liquid adhering to the surface of the substrate to be removed. In the method of irradiating and heating the liquid-dehydrated substrate to be heated and drying, during the liquid-removing treatment, the peripheral surface of the substrate to be processed is irradiated with light and reflected light or transmitted light from the surface is irradiated. A cleaning / drying treatment method, characterized in that when the detected signal level of the detection signal becomes substantially constant, it is determined that the liquid removal treatment is completed, and then the drying treatment is performed.