JPH02142129A - Wafer pretreatment method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pretreatment method for silicon wafers, compound semiconductor wafers, and masks (hereinafter, these three will be collectively referred to as wafers), and in particular, acid treatment, The present invention relates to a method of washing a wafer with pure water, removing one liquid, and drying the wafer after chemical processing such as alkaline processing and resist stripping processing.

[Conventional technology] Conventional 2. As a pretreatment method for silicon wafer masks after 11 treatments of this type, one silicon wafer mask in a cleaning tank is cleaned with pure water using an overflow cleaning method or an ultrasonic cleaning method, and then the silicon wafers supported on a carrier are , mask, N.

A gas injection device is set in a high-speed rotary machine (Sushi-sama〆Raiya) inside, and silicon wafer 1 is heated using centrifugal force.
A widely used method is to drain and dry the mask. At this time, in order to enhance the cleaning effect, a so-called rinser dryer, which is equipped with a pure water injection device within a high-speed rotating machine, is often used.

However, in this drain drying method using a high-speed rotary machine, dust generated from the rotating mechanism during rotation may adhere to the silicon wafer or mask, or adjacent silicon wafers or masks in the carrier may come into contact and cause chipping. In addition, there was a problem in that the chipped chips adhered to other silicon wafers and masks, causing contamination and reducing the product yield.Also, this method cannot be applied to compound semiconductor wafers.Why? This is because compound semiconductor wafers are extremely brittle and easily damaged, and cannot withstand high-speed rotation.

Japanese Patent Laid-Open No. 60-223130 discloses a method and apparatus that utilizes surface tension to solve the above-mentioned problems in pre-processing silicon wafers and masks. Its schematic configuration is shown in FIG. A cleaning tank 3 placed on a base] is filled with pure water, and a silicon wafer mask 5 supported in a carrier 4 held by clamping rods 6 is placed in the cleaning tank 3. Then the solicon wafer. The mask 5 is attached to the swing rod 7 and the plate member 8.
The carrier 4 is brought into contact with a rocking means consisting of the following, and the carrier 4 is pulled up at a very slow speed while being slightly rocked. This lifting is performed by a movable table 2 connected to a clamping rod 6 and driven by a driving means 9. During lifting, drying air is applied to the silicon wafer and mask 5 from a gas supply means (not shown). As a result, the surface tension of pure water is effectively utilized by the straining speed, and the pure water etc. adhering to the silicon wafer and mask 5 are reliably wiped away by the drying air, and the liquid is drained and dried from the silicon wafer mask 5. It can be performed. However, in this method, since the swinging means is brought into contact with the object to be processed and oscillated, it is difficult to apply this method to compound semiconductor wafers that are easily damaged as described above.

As a method to solve the problems mentioned above in pre-processing compound semiconductor wafers, IPA is applied to compound semiconductor wafers.
A well-known method is to apply vapor of (isopropyl alcohol) to replace moisture adhering to a compound semiconductor wafer and dry it. This method is extremely effective in preventing the adhesion of dust particles.

[11B to be Solved by the Invention] Problems in the above-described wafer pretreatment method are as follows. That is, in the case of the method disclosed in Japanese Patent Application Laid-open No. 60-223130, not only is a complicated structure of swinging means and driving means required, but the driving means is placed above the silicon wafer and mask that are the objects to be processed. Because of this, there was a problem in that dust generated in the driving means fell and was attached to the silicon wafer and mask.

On the other hand, in the case of a method using IPA, IPA vapor is highly explosive, so IPA is used to monitor its concentration.
There is a problem that not only is FF necessary, but also that it may pose a danger to workers in the event of an emergency.

The purpose of this invention is to eliminate the above-mentioned conventional problems and improve the device. j! without clutter, without dust adhering to the wafers, and without causing danger to workers.
It is an object of the present invention to provide a wafer pretreatment method that can perform cleaning with pure water, draining the liquid, and drying the wafer after chemical treatment of the wafer.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, as a first means, after cleaning with a chemical solution supported on a carrier in a cleaning tank installed in a clean air atmosphere and filled with pure water, In a wafer pretreatment method in which the wafer is immersed, cleaned, drained, and dried, the water level of the pure water in the cleaning tank in which the wafer is immersed is drained at a very low speed by draining the water using a drainage means. In addition to draining the wafer by lowering it, a dry inert gas is supplied from the gas supply means to the cleaning tank from just before the water level is lowered to the top of the wafer until the wafer is removed from the cleaning tank after a predetermined period of time after the water has drained. It is assumed that the wafer is dried by injecting gas in an amount corresponding to the volume of pure water reduced by slow drainage.

In addition, as a second means, after using the first means, the wafer is heated by a heating means provided in the cleaning tank until the wafer is taken out from the cleaning tank after a predetermined period of time after the water draining is completed. and dry.

As a third method, the wafer is cleaned by immersing the wafer after cleaning with a chemical solution supported on a carrier in a cleaning tank installed in a clean air atmosphere and filled with pure water.
In a pretreatment method for wafer λ that involves draining and drying, the water level of pure water in a cleaning tank in which a wafer is immersed is drained by draining means and lowered at a very slow speed to drain the wafer. The wafer is heated and dried by a heating means provided in the cleaning tank until the wafer is taken out from the cleaning tank after a predetermined period of time after the water draining is completed.

Furthermore, as a fourth means, while supplying pure water into the cleaning tank from a water supply port provided in the cleaning tank and causing the pure water to overflow from the cleaning tank, ultrasonic waves are generated from an ultrasonic generation means provided in the cleaning tank. The wafer is cleaned by applying ultrasonic vibration to the wafer, and when the cleaning is completed, the supply of pure water is stopped, and then the above-mentioned step 1. Second. One of the third means shall be taken.

Furthermore, as a fifth means, an infrared heater is used as the heating means in each of the above means.

Note that the cleaning tank and carrier are preferably made of quartz glass. Further, as the dry inert gas, N gas is preferable. Furthermore, from the point of view of effective use of surface tension, the speed of slow-speed drainage is such that the movement of water level is 3 cm/si.
A speed that is less than or equal to n is preferable.

[Effect]

According to the above-mentioned first means, since the water level of the pure water in which the wafer is immersed is lowered at a very slow speed, surface tension is generated on the wafer surface, thereby easily realizing liquid drainage. Furthermore, when the wafer surface and pure water are separated due to this surface tension, so-called peeling electrification occurs. This separation electrification causes a repulsive force to act between the wafer and the particles in the pure water, thereby preventing the particles in the pure water from adhering to the wafer surface and contaminating the wafer during draining. Furthermore, since an inert gas is injected into the cleaning tank as the water level is lowered, the atmosphere around the wafer becomes an inert atmosphere, thereby preventing the formation of a natural oxide film on the wafer surface. As mentioned above, the method of the present invention utilizes the effect of surface tension, so when injecting inert gas into the cleaning tank, it is necessary to do so gently so as not to disturb the water surface. . The time it takes to take out the wafer from the cleaning tank after the draining is completed depends on the temperature of the clean air atmosphere in which the cleaning tank is located. This is because the temperature of the inert gas is often close to the temperature of this clean air atmosphere, and the degree of drying effect varies depending on the temperature of the inert gas.

Next, according to the above-mentioned second means, since the wafer is heated after the drainage is completed, the wafer can be dried more quickly than the first means.

Further, according to the third means described above, since an inert gas is not injected into the cleaning tank, although there is a possibility that a natural oxide film may be formed on the wafer surface, the device configuration is significantly simplified, and the liquid draining and Pretreatment such as drying can be performed.

Furthermore, according to the fourth means described above, draining the wafer,
Since the cleaning tank that performs drying also cleans the wafer, only one cleaning tank is required. Therefore, the wafer can be cleaned, drained, and dried without carrying out the troublesome handling operation of moving the carrier carrying the wafer to another cleaning tank.

If the cleaning tank and carrier are made of quartz glass, and the heating means is an infrared heater, which is the fifth means mentioned above, the radiant heat from the infrared heater will almost pass through the cleaning tank and carrier made of quartz glass, and will be considerably reduced. amount of heat is absorbed by the wafer.

In other words, only the wafer is heated, and the cleaning tank and carrier are not heated.When the cleaning tank and carrier are heated,
There is a risk that particles that have been adsorbed and trapped on the quartz glass surface will receive thermal energy and fly out into the surroundings, adhering to the wafer surface, but this danger can be prevented by using an infrared heater.

Furthermore, when a carrier made of quartz glass is used, the following effects occur. Commonly used Teflon carriers naturally become strongly negatively charged. As a result, the wafer surface becomes positively charged due to electrostatic induction. Positively charged particles and ions (for example, sodium ions) are attracted to negatively charged carriers. When these particles and the like adhere to the carrier, they undergo charge exchange on the carrier, move, and adhere to the wafer surface, contaminating the wafer. By using a carrier made of quartz glass, wafer contamination due to such causes can be prevented. Note that if a carrier made of Teflon is used, the carrier will be heated even when an infrared heater is used, so from this point of view as well, a carrier made of Teflon is inappropriate.

(Example) FIG. 1 shows a schematic diagram of the configuration of an apparatus for carrying out a wafer pretreatment method according to an embodiment of the present invention. Reference numeral 10 denotes a cleaning tank made of quartz glass, also not shown, in a clean room (not shown). It is installed in a clean draft. 11 is a carrier IJ also made of quartz glass. 7.12 is a wafer, 1
3 is a water supply port for supplying pure water to the cleaning tank 10 when cleaning the wafer 12 and filling the cleaning tank 10 with pure water; 14 is an inert gas Nu for drying the wafer 12; N for supplying gas! At the gas supply port, N Yogas is a liquid N placed in a clean room! It may be supplied from a cylinder or centrally piped from a tank outside the clean room. 15 is an infrared heater which is also a heating means used when drying the wafer 12, 16 is a lid used when injecting N gases into the cleaning tank 10, and 17 is a slow-speed drain of the pure water filled in the cleaning tank 10. and a metering drainage pump, which is a drainage means for draining liquid from the wafer, 18
An ultrasonic vibrator 19 is an ultrasonic generating means for applying ultrasonic vibration to the wafer 12 when cleaning the wafer 12.
is the surface of pure water. It is desirable that the specific resistance of pure water is about 18 MΩ-1.

In this embodiment, first, with the lid 16 removed, pure water is supplied from the water supply port 13 into the cleaning tank 10 to overflow, and the ultrasonic vibrator 18 is activated to generate ultrasonic vibrations. , the carrier 11 is placed on the bottom surface of the cleaning tank 10 in FIG. You can also tell them.

When the ultrasonic cleaning is finished, the pure water surface 1 in the cleaning tank 10
9 is above the top of the wafer 12, the water supply is stopped, and the lid 16 is attached to the cleaning tank IO.

Next, the metering drainage pump 17 is operated to drain the pure water, and the water surface 19 of the pure water is heated at a slow speed (for example, 3 cffi/win).
) to drain the liquid from the wafer 12. During this lowering, Nt gas is supplied from the N□ gas supply port 14 of the lid 16 immediately before the top of the wafer 12 is exposed from the water surface 19 to dry the wafer 12. This supply needs to be performed so as not to disturb the pure water surface 19 and to supply an amount of N8 gas corresponding to the volume of the drained pure water. At this time, the lid 16 is provided so that the N8 gas can be quietly injected into the cleaning tank 10 without introducing air into the cleaning tank θ and without disturbing the water surface 19. After the drainage is completed, the infrared heater is turned on and heating drying of the wafer 12 is started. As for the heating temperature, a range of 50°C to 250°C is suitable for the N1 gas temperature in the cleaning tank, and a range of 80°C to 180°C is more suitable.

If the heating temperature is too low, the time required for heating and drying will be longer; on the other hand, if the heating temperature is too high, the infrared heater 1
The time required to heat the gas 5 becomes longer, which in any case causes an increase in takt time. Note that the temperature of N and gas can be easily measured by a temperature sensor not shown. During heating, the temperature in the cleaning tank 10, that is, the temperature of N and gas increases as described above. Therefore, the N gas forms an upward current and tends to flow out of the cleaning tank 10. When the N□ gas flows out, air flows into the cleaning tank 10 and the wafer 12
A natural oxide film may be formed on the surface. Therefore, the amount of N and gas supplied during this heating drying must be set to a sufficient amount to prevent this air from flowing into the cleaning tank 1.
If the volume of 0 is 181, then 31 to 201/1n is appropriate. However, if the amount is too large, the N in the cleaning tank 10
t Gas temperature becomes non-uniform.

Note that the N8 gas supply during this heating and drying is performed separately below the bottom of the cleaning tank 10, since the drainage has already been completed.
A rich gas supply port may be provided, and N8 gas may be supplied into the cleaning tank 10 from this supply port through the bottom surface of the cleaning tank 10.

〔Effect of the invention〕

As described above, according to the present invention, in the wafer pretreatment method after chemical treatment, the wafer liquid is drained by draining pure water from the cleaning tank at a very low speed, and the wafer drying is performed using an inert gas. The wafer is further cleaned by pouring it into the cleaning tank and heating and drying it with a heating means, and then draining the wafer.

Since the ultrasonic cleaning was carried out in the same cleaning tank as the one used for drying, the following effects were achieved.

■Wafer pretreatment is possible with an extremely simple equipment configuration.

■Wafer pretreatment is possible without any dust particles adhering to the wafer.

■Wafer pretreatment is possible without posing any danger to workers.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for performing a wafer preprocessing method according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of an apparatus for performing conventional preprocessing. 10: Cleaning tank, 11: Carrier, 12: Wafer, 13:
Water supply port, 14FN! Gas supply port, 15: infrared heater,
16: Lid, 17: Stationary drainage pump, 18: Ultrasonic vibrator, 19: Water surface. I4-2 Kasui joint descendant system 1 Figure

Claims (1)

[Claims] 1) A wafer cleaned with a chemical solution supported on a carrier is immersed in a cleaning tank installed in a clean air atmosphere and filled with pure water, and the wafer is cleaned and drained. In a method for pre-processing a wafer for drying, the water level of the pure water in the cleaning tank in which the wafer is immersed is drained by draining means and lowered at a slow speed to drain the wafer. At the same time, from just before the water level is lowered to the top of the wafer until the wafer is taken out from the cleaning tank after a predetermined period of time after drainage is completed, dry inert gas is supplied from the gas supply means into the cleaning tank. A method for preprocessing a wafer, characterized in that the wafer is dried by injecting the pure water in an amount corresponding to the volume of the pure water reduced by slow drainage. 2) In the wafer pretreatment method according to claim 1, the wafer is heated by a heating means provided in the cleaning tank until the wafer is taken out from the cleaning tank after a predetermined time from the time when drainage is completed; A wafer pretreatment method characterized by drying. 3) The wafer is cleaned, drained, and dried by immersing the wafer after cleaning with a chemical solution supported on a carrier in a cleaning tank installed in a clean air atmosphere and filled with pure water. In the pretreatment method, the water level of the pure water in the cleaning tank in which the wafer is immersed is drained by a draining means and lowered at a slow speed to drain the wafer, and the water draining is completed. heating the wafer by a heating means provided in the cleaning tank until the wafer is taken out from the cleaning tank after a predetermined time from the time when the wafer is removed;
A wafer pretreatment method characterized by drying. 4) In the wafer pretreatment method according to claim 1 or 3, while supplying pure water into the cleaning tank from a water supply port provided in the cleaning tank and causing the pure water to overflow from the cleaning tank, An ultrasonic wave is generated from an ultrasonic generating means provided in the cleaning tank, and the ultrasonic vibration is applied to the wafer to clean the wafer, and then the supply of the pure water is stopped, and the pure water is drained at a slow speed. A wafer pretreatment method characterized by starting. 5) The wafer pre-processing method according to claim 2 or 3, wherein the heating means is an infrared heater.