JP2008182188A - Cleaning fluid for electronic material and cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide cleaning liquid for electric materials and a cleaning method for efficiently cleaning and removing particle components or the like on a wafer surface, and for preventing re-contamination. <P>SOLUTION: This cleaning method is characterized to use cleaning liquid using ultra-pure water or hydrogen water as raw material water in combination with ultrasonic irradiation under the presence of hydrogen micro-bubbles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning solution for an electronic material, particularly a silicon wafer, and a cleaning method using the same.

  In recent years, semiconductor LSI manufacturing technology using a silicon wafer requires the use of a larger diameter wafer and a finer processing technology. Furthermore, it is also necessary to solve problems such as maintenance and improvement of product quality and reduction of production cost due to complicated processes.

  In particular, in many fields of semiconductor LSI manufacturing technology using silicon wafers, so-called wet processing steps including processing with various solutions are indispensable steps. A particularly important step among such wet treatment steps is a cleaning step. In the conventional cleaning process, improvements have been made mainly in the selection of the component composition of the cleaning liquid, or their concentration, cleaning temperature, cleaning time, etc. Technology "Realize (2000)). However, these conventional techniques have not been sufficient to satisfy the demands associated with the recent need for finer processing techniques, complicated processes, higher cleaning, and lower costs. Furthermore, in recent years, due to demands for stricter environmental protection measures and lower costs for waste liquid treatment, dilute chemical cleaning, chemical-less cleaning, and the like have been desired.

  As a method for solving these problems, so-called functional water typified by ozone water and hydrogen water has been vigorously researched and developed, and its practical application is progressing. Ozone water has been put into practical use in a wide range of semiconductor cleaning to remove metal impurity contamination and organic contamination. Hydrogen water is also applied to glass substrate cleaning of liquid crystal displays for the purpose of particle removal (for example, supervised by Masayuki Toda, edited by Japan Industrial Cleaning Council, "Functional Water Learned from the Beginning" Industry Research Committee (2002)).

  Hydrogen water is expected as an alternative to ammonia + hydrogen peroxide (hereinafter referred to as “APM”), which is widely applied as a particle removal cleaning liquid in the field of semiconductor cleaning. Hydrogen water is very advantageous in terms of chemical cost compared to APM, but has poor particle removal capability. Hydrogen water has been put into practical use because it has a sufficient cleaning level for cleaning glass substrates for liquid crystal displays, but has not yet been put into practical use in the field of semiconductor cleaning such as silicon wafers due to lack of cleaning capability.

  Therefore, it is necessary to further increase the capacity of hydrogen water and develop a low-cost APM alternative technology for semiconductor cleaning.

  The present invention provides a completely new method applicable to all silicon wafer cleaning processes.

  As a result of earnest research and development of a new cleaning liquid and a cleaning processing method using the same that can meet the recent strong demands for cleaning processing of silicon wafers, the present inventors have surprisingly found that ultrapure water or hydrogen water. It was found that this can be solved by using a cleaning liquid combined with ultrasonic irradiation in the presence of hydrogen microbubbles in the presence of hydrogen microbubbles, and the present invention has been completed.

  That is, the cleaning liquid for electronic materials of the present invention is characterized by containing microbubbles by hydrogen gas, and is an aqueous liquid to which ultrasonic vibration is applied.

  In the electronic material cleaning liquid of the present invention, the aqueous liquid is ultrapure water or hydrogen water.

  The cleaning method of the present invention is a method characterized by using such a cleaning liquid, and is characterized by being performed in an aqueous liquid in which hydrogen microbubbles are present and under ultrasonic irradiation.

  In the cleaning method of the present invention, the aqueous liquid is ultrapure water.

  In the cleaning method of the present invention, the aqueous liquid is hydrogen water.

  The cleaning method of the present invention is characterized in that an alkali is further added to the aqueous liquid.

  The cleaning method of the present invention is characterized in that alkali and hydrogen peroxide are added to the aqueous liquid.

  The cleaning method of the present invention is characterized in that a surfactant is added to the aqueous liquid material.

  In the cleaning method of the present invention, the alkali to be added contains at least one of sodium hydroxide, potassium hydroxide, ammonia, tetramethylammonium hydroxide (hereinafter referred to as “TMAH”), and choline. To do.

  Furthermore, the cleaning method of the present invention is characterized in that the electronic material is a silicon wafer.

  By performing the cleaning process using the cleaning liquid of the present invention, it is possible to efficiently clean and remove particle components and the like on the wafer surface and prevent recontamination.

  The cleaning liquid for electronic materials of the present invention is an aqueous liquid containing microbubbles by hydrogen gas, and is an aqueous liquid to which ultrasonic vibration is applied. The aqueous liquid is ultrapure water or hydrogen water. Further, the electronic material cleaning liquid of the present invention includes those to which various additives are added in order to obtain desirable characteristics. Here, as an electronic material that can be cleaned with the cleaning liquid of the present invention, a silicon wafer is particularly mentioned.

  The cleaning method of the present invention is characterized by using the cleaning liquid of the present invention described above. That is, the electronic material is performed in an aqueous liquid containing hydrogen microbubbles and under ultrasonic irradiation.

Electronic material The electronic material that can be cleaned by the cleaning method of the present invention is not particularly limited in material, shape, and the like. Various materials used in conventional semiconductor manufacturing are included. Specifically, Si, Ge, As, or a composite material thereof can be given. Further, in the present invention, the shape of the electronic material includes various conventionally known shapes and shapes formed in various manufacturing processes. In the present invention, the shape of the wafer is particularly preferably usable. Particularly preferred are silicon wafers at each stage used in a normal silicon wafer production process and a silicon cleaning process at each stage of the semiconductor production process to the silicon wafer.

Aqueous liquid The aqueous liquid of the present invention means a liquid that can contain microbubbles of hydrogen gas and can be vibrated by ultrasonic waves and contains at least water. Further, it is preferable that no unnecessary impurities are contained when cleaning the electronic material, and a conventionally used cleaning liquid for electronic material can be used. In the present invention, it is particularly preferable to use ultrapure water. Further, the ultrapure water may be degassed in advance to remove the dissolved gas. As a method for degassing ultrapure water, a vacuum membrane degassing method or the like can be applied.

  In the present invention, it is preferable to use hydrogen water as the aqueous liquid. There is no restriction | limiting in particular about the preparation method of the hydrogenous water which can be used by this invention, The hydrogenous water manufactured with the well-known hydrogen water manufacturing apparatus can be used. Here, as a known hydrogen water production apparatus, there is specifically a method of producing hydrogen gas dissolved in ultrapure water degassed through a gas permeable membrane (eg, supervised by Masayuki Toda, Japan). Industrial Cleaning Council, “Functional Water Learned from the Beginning” Industry Research Committee (2002)).

  Further, the hydrogen concentration in the cleaning liquid of the present invention is not particularly limited, and the volume and shape of the cleaning apparatus, the number of silicon wafers, the installation method, the cleaning liquid temperature, the cleaning time, other additives for the cleaning liquid, and the simultaneous use described below. The concentration can be appropriately selected within a preferable range based on hydrogen microbubbles or ultrasonic irradiation conditions.

Hydrogen microbubbles There are no particular restrictions on the method of preparing hydrogen microbubbles used in the cleaning method of the present invention, and hydrogen gas is introduced using a known microbubble generation method or generator to generate microbubbles in the cleaning liquid. Can be made. Various methods described in the literature can be applied to known methods for generating microbubbles (for example, Tomoaki Kamiyama and Makoto Miyamoto, “World of Microbubbles” Industrial Research Committee (2006)). Moreover, about a well-known microbubble generator, a high-speed shear flow type microbubble generator is mentioned.

  There are no particular restrictions on the conditions for generating hydrogen microbubbles and the amount of hydrogen microbubbles generated in the cleaning method of the present invention. Hydrogen microbubbles in a preferable range as appropriate based on the volume, shape, number of silicon wafers used, installation method, cleaning liquid temperature, cleaning time, other additives for cleaning liquid, and ultrasonic irradiation conditions used simultaneously described below. The generation amount can be selected.

  Further, the hydrogen of the hydrogen microbubble of the present invention includes not only hydrogen but also cases where other components are contained in hydrogen. Specific examples of other components include air, helium, nitrogen, oxygen, and argon.

  Further, the position where hydrogen microbubbles are generated is not particularly limited, and the nozzle part of hydrogen microbubbles can be provided at any position of the cleaning container. Select a preferred position as appropriate based on the volume and shape of the cleaning device used, the number of silicon wafers, the installation method, the cleaning liquid temperature, the cleaning time, other additives for the cleaning liquid, and the ultrasonic irradiation conditions used at the same time described below. Can do. Specifically, the bottom part, the side part, the upper part of the cleaning container, or a plurality of parts thereof can be mentioned.

  It is also possible to generate hydrogen microbubbles in a container different from the cleaning container and then introduce the hydrogen microbubbles into the cleaning container using a water pump. Further, it is possible to connect the cleaning container and the hydrogen microbubble water production container with a circulation pipe and continue the circulation with the water pump. Further, it is possible to install a hydrogen microbubble generator in the middle of the water supply pipe and introduce hydrogen microbubble water into the cleaning container.

Ultrasonic irradiation The ultrasonic irradiation method and apparatus for applying ultrasonic vibration of the present invention are not particularly limited, and the cleaning liquid is irradiated with ultrasonic waves using a known ultrasonic irradiation method or ultrasonic irradiation apparatus. be able to.

  There are no particular restrictions on the generation conditions of ultrasonic waves used in the cleaning method of the present invention, such as frequency and generated power. A preferable range can be appropriately selected based on the volume and shape of the cleaning device to be used, the number of silicon wafers, the target cleaning process, the installation method, the cleaning liquid temperature, the cleaning time, and other additives of the cleaning liquid.

  What is necessary is just to select the thing of the preferable range suitably for the frequency of the ultrasonic wave to be used by the washing | cleaning process to be used, the particle size of the removal object, etc. Specifically, the ultrasonic frequency is preferably in the range of 20 to 2000 kHz. If the frequency is lower than this range, the so-called ultrasonic region may be deviated and the effect may be reduced. Moreover, when it is higher than this range, a sufficient cleaning effect cannot be obtained. In addition, even if it is the said frequency range, when an ultrasonic frequency is low, there exists a possibility that a damage | wound may generate | occur | produce in a washing | cleaning target object by ultrasonic irradiation. In a process where generation of scratches due to ultrasonic irradiation becomes a problem, for example, in a silicon wafer cleaning process after the polishing process, the frequency is preferably 700 kHz or more. The output may be 100 to 1000 W, but is not particularly limited, and the number of vibration elements to be installed may be selected for each size and design of the cleaning device and each purpose of the cleaning process.

  Also, there is no particular limitation on the position where the ultrasonic wave is irradiated, and the ultrasonic wave generation direction can be provided at any position of the cleaning container. A preferable position can be selected as appropriate based on the volume and shape of the cleaning apparatus to be used, the number of silicon wafers, the installation method, the cleaning liquid temperature, the cleaning time, and other additives of the cleaning liquid. Specifically, a method of irradiating from the bottom part, the side part, the upper part, or a plurality of parts of the cleaning container can be mentioned.

Other Additive Components Other components may be added to the cleaning liquid used in the cleaning method of the present invention. For example, alkali and surfactant are mentioned. Particularly preferred additives for alkali include sodium hydroxide, potassium hydroxide, ammonia, TMAH and choline. There is no restriction | limiting in particular about the kind of these additives, and addition amount. The volume and shape of the cleaning apparatus to be used, the number of silicon wafers, the installation method, the cleaning liquid temperature, the cleaning time, hydrogen microbubbles, ultrasonic irradiation, and the like can be selected as appropriate.

  By adding an appropriate amount of hydrogen peroxide to the alkali, it is possible to improve the particle removal capability, to make the wafer surface hydrophilic, and to prevent surface roughness (haze).

Silicon wafer during cleaning The cleaning method of the present invention can very effectively remove particle contamination on the surface of a silicon wafer, and, surprisingly, recontamination due to particles or the like is prevented.

  Hereinafter, the cleaning method of the present invention will be described in more detail based on specific examples, but the present invention is not limited to these examples.

(Example 1-1)
Sample: diluted with hydrofluoric acid, spin-dried to remove natural oxide film, and a hydrophobic solution containing abrasive solution (Fujimi Chemical GLANZOX3900 diluted 10 million times) on the surface of a P-type mirror silicon wafer 10 mL was spin-coated and contaminated with an abrasive. Here, the amount of particle contamination was adhesion of 5000 to 10000 particles having a diameter of 0.13 μmφ or more. The number of particles was measured using Surfscan 6220 manufactured by KLA-Tencor.

Raw material liquid: ultrapure water Cleaning method: The cleaning liquid was continuously introduced into the 40 L cleaning tank at 6 L / min and continued to overflow. One nozzle part of a microbubble generator (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) was provided at the bottom of the washing tank, and 1 L / min microbubbles were continuously generated. Hydrogen gas was used as the bubble gas. Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles were continuously generated during the cleaning. In addition, ultrasonic waves having a frequency of 1 MHz and an output of 1 kW were applied throughout the cleaning. The dissolved hydrogen concentration of the cleaning liquid during cleaning was 0.5 ppm.

  The sample was immersed here at a liquid temperature of 20 ° C. for 5 minutes. Thereafter, the sample was taken out, put into an ultrapure water tank, and rinsed at 20 ° C. for 5 minutes. The sample was then spin dried.

  For the measurement of the number of particles of the sample wafer after cleaning, Surfscan 6220 manufactured by KLA-Tencor Corporation was used. A particle removal rate of 0.13 μmφ or more was determined from the number of adhered particles before and after cleaning.

(Example 1-2)
It is the same as that of an Example except a raw material liquid being 1.4 ppm hydrogen water. Hydrogen water was produced by dissolving hydrogen gas in ultrapure water degassed under reduced pressure through a gas permeable membrane. The dissolved hydrogen concentration in the cleaning liquid during cleaning was 1.5 ppm.

(Comparative Example 1-1)
Example 1-2 is the same as Example 1-2 except that hydrogen microbubbles are not introduced. The dissolved hydrogen concentration in the cleaning liquid during cleaning was 1.4 ppm.

(Comparative Example 1-2)
It is the same as that of Example 1-1 except not irradiating an ultrasonic wave. The dissolved hydrogen concentration of the cleaning liquid during cleaning was 0.5 ppm.

(Example 2-1)
Example 1-1 is the same as Example 1-1 except that the raw material solution contains 15 mM ammonia and 30 mM hydrogen peroxide.

(Example 2-2)
Example 1-2 is the same as Example 1-2 except that the raw material solution contains 15 mM ammonia and 30 mM hydrogen peroxide.

(Comparative Example 2)
The same as Comparative Example 1-1 except that the raw material solution contains 15 mM ammonia and 30 mM hydrogen peroxide.

(Example 3-1)
The sample was a silicon wafer immediately after CMP (more than 2 million particles of 0.13 μmφ or larger), and the same as Example 1-1 except that the raw material liquid contained 10 mM-TMAH and 30 mM-hydrogen peroxide. It is.

(Example 3-2)
The sample is a silicon wafer immediately after CMP (more than 2 million particles having a diameter of 0.13 μmφ or more), and is similar to Example 1-2 except that the raw material liquid contains 10 mM-TMAH and 30 mM-hydrogen peroxide. It is.

(Comparative Example 3)
Similar to Comparative Example 1-1, except that the sample is a silicon wafer immediately after CMP (more than 2 million particles having a diameter of 0.13 μmφ or more), and the raw material solution contains 10 mM-TMAH and 30 mM-hydrogen peroxide. It is.

(Example 4-1)
In order to confirm the re-adhesion behavior of the removed particles, in the cleaning test of Example 3-1, a silicon wafer with a clean surface (previously dried with dilute hydrofluoric acid and dried to remove the natural oxide film and remove the hydrophobic surface In the same washing carrier. The number of adhered particles after washing was measured.

(Example 4-2)
In order to confirm the re-adhesion behavior of the removed particles, in the cleaning test of Example 3-2, a silicon wafer with a clean surface (previously dried with dilute hydrofluoric acid and dried to remove the natural oxide film and remove the hydrophobic surface In the same washing carrier. The number of adhered particles after washing was measured.

(Comparative Example 4)
In order to confirm the re-adhesion behavior of the removed particles, in the cleaning test of Comparative Example 3, a silicon wafer with a clean surface (previously dried with dilute hydrofluoric acid and dried to remove the natural oxide film to obtain a hydrophobic surface) In the same washing carrier. The number of adhered particles after washing was measured.

(Examples 5-1 to 5-12)
Sample: 1N-hydrochloric acid solution in which silicon nitride powder (particle size distribution peak: 500 nm) is dispersed in a 200 mm diameter P-type mirror silicon wafer having a hydrophobic surface after washing with diluted hydrofluoric acid and spin drying to remove a natural oxide film It was immersed in and silicon nitride particles were adhered.

  Here, the amount of particle contamination was adhesion of 5000 to 10,000 particles having a size of 0.1 μmφ or more. Hitachi High-Technologies LS6500 was used for the particle number measurement.

  Cleaning solution: In each example, a cleaning solution prepared to contain TMAH and hydrogen peroxide having the concentrations shown in Table 3 was used.

  Cleaning method: A 40 L cleaning tank is filled with a liquid containing TMAH and hydrogen peroxide having a predetermined concentration shown in Table 3, and the nozzle part of the microbubble generator (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) is installed. One was installed at the bottom of the washing tank, and 1 L / min microbubbles were continuously generated. Hydrogen gas was used as the bubble gas. Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles were continuously generated during the cleaning. The dissolved hydrogen concentration of the cleaning liquid during cleaning was 0.5 ppm. In addition, ultrasonic waves having a frequency of 1 MHz and an output of 1 kW were applied throughout the cleaning.

  The sample was immersed here at a liquid temperature of 60 ° C. for 5 minutes. Thereafter, the sample was taken out, put into an ultrapure water tank, and rinsed at 20 ° C. for 5 minutes. The sample was then spin dried.

  LS6500 manufactured by Hitachi High-Technologies was used for particle measurement of the sample wafer before and after cleaning. The particle removal rate of 0.1 μmφ or more was determined from the number of particles attached before and after cleaning.

(Comparative Example 5)
The same as Examples 5-1 to 5-12, except that APM (ammonia 4700 ppm, hydrogen peroxide 31000 ppm) was used as the cleaning liquid, and hydrogen microbubbles were not used.

(result)
Tables 1 to 3 summarize the implementation conditions and the results obtained.

  The following can be understood from Tables 1 to 3.

  It can be seen that the surface contamination is remarkably removed by washing under ultrasonic irradiation in the presence of hydrogen microbubbles. In Example 1-1, although the concentration of dissolved hydrogen is lower than that of Comparative Example 1-1, it can be seen that the effect of microbubbles appears because the cleaning ability is high. Moreover, the removal capability is further improved by keeping the solution alkaline. Moreover, it turns out that surface roughness (haze) can be prevented by adding hydrogen peroxide.

  It can be seen from Table 3 that by introducing hydrogen microbubbles into TMAH 800 ppm and hydrogen peroxide 500 ppm, there is a cleaning ability equivalent to that of APM without ammonia microbubbles (ammonia 4700 ppm, hydrogen peroxide 31000 ppm). That is, it can be seen that the chemical concentration can be significantly reduced by introducing hydrogen microbubbles. It can also be seen that increasing the TMAH concentration improves the cleaning ability.

  From the results of Examples 4-1 and 4-2 and Comparative Example 4, by adding hydrogen microbubbles, reattachment of particles that are removed from the wafer surface and exist in the cleaning liquid in the water tank is remarkably suppressed. I understand that.

  Thereby, the removal capability of the particle | grains on a wafer surface can be expected.

  The silicon wafer cleaning liquid and cleaning method according to the present invention can be applied to all silicon wafer cleaning processes that have been performed so far.

Claims (11)

  A cleaning liquid for electronic materials, characterized in that it is a water-based liquid containing microbubbles by hydrogen gas and imparted with ultrasonic vibration.   The cleaning liquid for electronic materials according to claim 1, wherein the aqueous liquid is ultrapure water.   The cleaning liquid for electronic materials according to claim 1, wherein the aqueous liquid is hydrogen water.   A method for cleaning an electronic material, which is performed in an aqueous liquid containing hydrogen microbubbles and under ultrasonic irradiation.   The method for cleaning an electronic material according to claim 4, wherein the aqueous liquid is ultrapure water.   5. The electronic material cleaning method according to claim 4, wherein the aqueous liquid is hydrogen water.   The method for cleaning an electronic material according to any one of claims 4 to 6, wherein an alkali is further added to the aqueous liquid.   The method for cleaning an electronic material according to claim 4, wherein alkali and hydrogen peroxide are added to the aqueous liquid.   The method for cleaning an electronic material according to claim 4, wherein a surfactant is added to the aqueous liquid.   9. The electronic material cleaning according to claim 7, wherein the alkali to be added contains at least one of sodium hydroxide, potassium hydroxide, ammonia, tetramethylammonium hydroxide (TMAH), and choline. Method.   The method for cleaning an electronic material according to claim 4, wherein the electronic material is a silicon wafer.