JP2008103701A - Wet treatment method of silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet treatment method of a silicon wafer. <P>SOLUTION: The method of performing wet treatment on a silicon wafer is characterized in being performed under presence of micro bubbles. Organic components, particle components and the like on a surface of the wafer can be efficiently washed and removed. Furthermore, a speed of etching in washing can be freely controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wet processing method for a silicon wafer.

  In recent years, semiconductor LSI manufacturing technology using silicon wafers requires the use of larger diameter wafers and 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. Among such wet processing steps, particularly important steps are a cleaning step, an etching step, and the like. Conventionally, in these wet processing steps, improvements have been repeated mainly in terms of selection of the type, concentration, processing temperature, time, etc. of the solution (for example, edited by Hajime Hattori, “New Silicon Wafer Surface Cleaning 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.

  The present invention provides a completely new method applicable to all wet processing of silicon wafers.

  As a result of earnest research and development of a new processing method capable of satisfying the recent strong demand for wet processing of silicon wafers, the present inventors surprisingly changed the conventional silicon wet processing process in the presence of microbubbles. It has been found that the problem can be solved by carrying out the invention, and the present invention has been completed.

  That is, the present invention relates to a method for wet-treating a silicon wafer, which is performed in the presence of microbubbles in a method for wet-treating a silicon wafer.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is post-slice cleaning processing.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is a particle removal cleaning process using APM (ammonia + hydrogen peroxide) of the silicon wafer.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is a particle removal cleaning process with hydrogen water of the silicon wafer.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is a residue removal cleaning processing after lapping processing.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is oil-based ink removal cleaning processing.

  The wet processing method for a silicon wafer according to the present invention is particularly characterized in that the wet processing is a cleaning processing accompanied with etching of silicon.

  By wet-treating a silicon wafer in the presence of microbubbles with the method of the present invention, it becomes possible to efficiently clean and remove organic components, particle components and the like on the wafer surface. Furthermore, the etching rate can be freely controlled by the method of the present invention when performing a cleaning process with silicon etching in the presence of microbubbles.

(Silicon wet processing)
The processing method of the present invention is characterized in that the silicon wafer wet processing is performed in the presence of microbubbles. Therefore, there is no limitation on the type of silicon wafer wet processing to which the processing method of the present invention can be applied, and various conventionally known processing steps for wet processing of silicon wafers are included. Specifically, cleaning processes at various stages and etching processes using various purposes and conditions are included. Further, the conditions for these steps do not need to be changed.

  The cleaning process includes a cleaning process after cutting a wafer from a silicon ingot, a cleaning process after lapping, a cleaning process after rough polishing, a cleaning process after edge polishing, and a cleaning process after etching. The cleaning process after the finish polishing process, the cleaning process before and after the various annealing processes, the cleaning process before and after the epitaxial layer deposition, the final cleaning process before shipment, and the cleaning process between various other processes are included.

  The cleaning process to which the method of the present invention is more preferably applied is that the wet process is a cleaning process after slicing, a particle removing cleaning process using APM (ammonia + hydrogen peroxide) of a silicon wafer, a particle removing cleaning process using hydrogen water, and a lapping process. This is a cleaning process for removing the residue.

  Furthermore, for cleaning treatments involving silicon etching, cleaning solutions containing various alkalis such as ammonia, tetramethylammonium hydroxide, sodium hydroxide and potassium hydroxide, and various cleaning solutions containing fluorine such as hydrofluoric acid and ammonium fluoride are used. Examples of the cleaning process to be used.

(Micro bubble)
A feature of the processing method of the present invention is that the conventional silicon wafer wet processing is performed in the presence of microbubbles. Here, the microbubble generally means a fine bubble having a diameter of the order of micrometers, and is well known (for example, Tomoaki Kamiyama and Makoto Miyamoto, “The World of Microbubble”, published by the Industrial Research Society (2006). )reference). In particular, the diameter is in the range of 10 to several hundred μm. In particular, bubbles with a diameter of 60 μm or less exist for a long time with a low floating speed in the liquid. In addition, it is known that bubbles of this size gradually contract because the surface tension is stronger than the expansion force, and some bubbles eventually dissolve in the liquid. In addition, it has been pointed out that at the final stage of shrinkage, the inside becomes high temperature and high pressure, and special chemical species are generated or a shock wave is generated at the time of rupture. Further, the present invention is not particularly limited to the degree of bubble size distribution. Also included are fine bubbles having a substantially single distribution and fine bubbles having a plurality of distributions of various sizes. It also includes the case where the bubble size varies during the processing step. Further, the gas in the microbubbles is not particularly limited. The microbubble gas may be a single component or a mixed component gas. It can be appropriately selected depending on the microbubble generator. Specific gases include component gases of solution, air, hydrogen, oxygen, nitrogen, carbon dioxide, ozone, fluorine, chlorine, bromine, iodine, argon, and helium.

  There are no particular limitations on the method and apparatus for generating microbubbles that can be preferably used in the treatment method of the present invention. Any method and apparatus capable of generating microbubbles having the above-described properties can be used. Specifically, the method and apparatus described in Republication 00-69550 can be used.

(Sonication)
The feature of the treatment method of the present invention is that the conventional silicon wafer wet treatment is performed in the presence of microbubbles, but a preferable result may be obtained by using ultrasonic treatment together. Here, the ultrasonic processing method and apparatus are not particularly limited, and a conventional method and apparatus usable for wet processing of a silicon wafer can be preferably used. Specific examples include a frequency of 10 kHz to 2 MHz and an output of 100 to 1000 W, but there is no particular limitation. The number of vibration elements to be installed may be selected for each cleaning device and each purpose of the cleaning process. .

(Processing method)
The treatment method of the present invention may be performed in the presence of microbubbles in a commonly known silicon wafer wet treatment step. There are no restrictions on the presence of microbubbles, a method of pre-existing microbubbles in the solution of the wet treatment step, a method of continuously (or intermittently) introducing microbubbles into the solution during the wet treatment step, A method in which microbubbles are previously present in the solution of the wet treatment step and the microbubbles are continuously (or intermittently) introduced into the solution also during the wet treatment step is possible. Moreover, it is also possible to provide a microbubble generating tank separately from the cleaning tank and introduce a cleaning liquid containing microbubbles produced in the microbubble generating tank into the cleaning tank through a pipe or the like.

  As a cleaning method, not only a method of immersing a silicon wafer to be cleaned in a cleaning tank, but also a method of performing single wafer processing by spraying a processing liquid containing microbubbles by spraying or showering is possible.

  There are no particular restrictions on the type and amount of microbubbles present, and the microbubbles can be appropriately selected and optimized depending on the type of processing step. Specifically, microbubbles containing a preferred type of gas can be present in a preferred amount for a preferred time.

  In addition, it is possible to appropriately select the introduction location of the microbubbles according to the shape of the apparatus used in the wet treatment process. Depending on the shape of the device, a preferred type and amount of microbubbles can be present at a specific location within the device. Specifically, it is possible to provide a preferred number of microbubble generators at preferred locations in the apparatus.

  In addition, the treatment method of the present invention can be used in combination with ultrasonic treatment. The ultrasonic treatment can be preferably used in the mode used in the conventional wet treatment. For example, an ultrasonic generator can be provided inside or outside the wet processing apparatus. The wavelength and output of the ultrasonic wave can also be selected as appropriate. However, the combined use of microbubbles and sonication does not necessarily show a positive effect, and may reduce the cleaning ability.

  Hereinafter, although the processing method of this invention is demonstrated in more detail based on a specific Example, this invention is not limited to these examples.

  The microbubble device used below was M2-MS type manufactured by Nano Planet Research Laboratories. The amount of microbubbles generated and the type of gas were controlled by the type and flow rate of gas supplied to the microbubble device. Moreover, 90% or more of the bubbles generated in the following examples had a diameter of 60 μm or less, and had a frequency peak at a diameter of about 30 μm.

(Example 1) Cleaning after slicing Sample: A silicon wafer having a diameter of 200 mm obtained by cylindrical grinding of a silicon ingot manufactured by the CZ method was sliced using a multi-wire saw to obtain a silicon wafer having a thickness of about 800 μm. A mixture of silicon chips (powder), glycol, and abrasive (SIC powder) was adhered as a slurry on the sample surface.

  Cleaning chemical: Castrol No. 200 (0.1-1 wt% -KOH + surfactant (2-5 wt% -polyoxyethylene nonylphenyl ether)) was used at two levels of concentration: 20-fold diluted with ultrapure water and 200-fold diluted.

  Cleaning method: Put 6 L of chemical in the cleaning tank, and provide one microbubble generating part of the microbubble device (M2-MS / SUS type manufactured by Nano Planet Research Laboratories) at the bottom of the cleaning tank, 1 L / min microbubble Was generated. Air was used as the bubble gas.

  Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles continued to be generated during cleaning.

The sample was immersed here at a liquid temperature of 20 ° C. for 1 minute. Thereafter, the sample was taken out, placed in an ultrapure water tank, and rinsed at a liquid temperature of 20 ° C. for 1 minute. Thereafter, the sample was dried by spraying with dry air.
The chemical solution tank, the chemical solution composition, the chemical solution amount, the washing time, the rinsing time, the drying method, and the like were the same as in the examples, and the conditions that did not generate microbubbles were carried out as comparative examples.
Result: The degree of contamination on the sample surface was judged visually or by a photograph. The results are summarized in Table 1.

  From Table 1, it can be seen that surface contamination is remarkably removed by the presence of microbubbles.

(Example 2) Particle removal by APM (ammonia + hydrogen peroxide) Sample: APM-treated surface, DHF-treated surface, spin-dried, and a mirror-containing silicon wafer surface having a hydrophobic surface (Fujimi Chemical GLANZOX3900) The solution was diluted 10 million times with 10 mL of spin coating and contaminated with an abrasive. Here, the amount of particle contamination was adhesion of 3000 to 5000 particles having a particle size of 0.13 μmφ or more.

  Particle number measurement: Surfscan 6220 manufactured by KLA-Tencor Corporation was used.

  Cleaning solution: APM cleaning solution (29% ammonia: 31% hydrogen peroxide solution: ultrapure water = 1: 1: 5 (volume ratio)). Liquid temperature 60 ° C.

  Cleaning method: 40L of chemical solution is put in the cleaning tank, one nozzle part of the microbubble device (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) is provided at the bottom of the cleaning tank, and 1L / min microbubbles are placed. Generated. Air was used as the bubble gas.

  Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles continued to be generated during cleaning.

The sample was immersed here at 60 ° C. for 2 minutes. After that, the sample was taken out, placed in a 20 ° C. ultrapure water tank, and rinsed for 5 minutes. The sample was then spin dried.
The chemical solution tank, the chemical solution composition, the chemical solution amount, the washing time, the rinsing time, the drying method, and the like were the same as in the examples, and the conditions that did not generate microbubbles were carried out as comparative examples.

  Result: The particle removal rate is shown in FIG.

  It can be seen from FIG. 1 that the presence of microbubbles significantly improves the particle removal rate.

(Example 3) Particle removal with hydrogen water Sample: APM treatment of the surface followed by spin drying, and a mirror silicon wafer surface having a hydrophilic surface. A solution containing an abrasive (Fujimi Chemical GLANZOX3900 diluted 10 million times) 10 mL was spin-coated and contaminated with an abrasive. Here, the amount of particle contamination was adhesion of 500 to 800 particles having a diameter of 0.13 μmφ or more.
Particle number measurement: Surfscan 6220 manufactured by KLA-Tencor Corporation was used.

  Cleaning liquid: A hydrogen water cleaning liquid containing 1 to 1.4 ppm of dissolved hydrogen and 5 ppm of ammonia was used.

  Cleaning method: The chemical solution was continuously introduced into the 40 L cleaning tank at 6 L / min to overflow. One nozzle part of a microbubble device (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) was provided at the bottom position of the washing tank to generate 1 L / min microbubbles. Hydrogen was used as the bubble gas. Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles continued to be generated during cleaning. 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 20 ° C. for 2 minutes. Thereafter, the sample was taken out, placed in an ultrapure water tank, and rinsed at a liquid temperature of 20 ° C. for 5 minutes. The sample was then spin dried.
The chemical solution tank, the chemical solution composition, the chemical solution flow rate, the washing time, the ultrasonic irradiation conditions during washing, the rinse time, the drying method, and the like were the same as in the examples, and the conditions that did not generate microbubbles were carried out as comparative examples.
Result: The particle removal rate is shown in FIG.

  From FIG. 2, it can be seen that the presence of microbubbles significantly improves the particle removal rate.

(Example 4) Removal of residue after lapping treatment Sample: A 200 mm diameter silicon wafer prepared by lapping treatment was used. In order to evaluate the ability to remove the residue after the lapping treatment, about 0.1 ml of a liquid in which the components of the wrap oil were mixed was dropped on several portions of the wafer surface and dried. The dripped liquid is obtained by suspending about 100 g of an abrasive (Fujimi FO # 1200MR) in 100 mL of water with about 1 mL of a rust inhibitor (Shrek ECO # 500) and about 1 mL of a dispersant (Shrek # 600A-90) added. It has been made.

  Cleaning chemical: Castrol No. 200 (0.1-1 wt% potassium hydroxide + surfactant (2-5 wt% -polyoxyethylene nonylphenyl ether)) was diluted 20-200 times and used.

  Cleaning method: 4L of chemical solution is put in the cleaning tank, and one nozzle part of the microbubble device (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) is installed at the bottom of the cleaning tank, and 1L / min microbubbles are placed. Generated. Air was used as the bubble gas. Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles continued to be generated during cleaning.

The sample was immersed here at a liquid temperature of 20 ° C. for 5 minutes. After the sample was taken out, it was placed in a 20 ° C. ultrapure water bath and rinsed for 10 minutes. Thereafter, the sample was dried by blowing dry air.
The chemical solution tank, the chemical solution composition, the chemical solution amount, the washing time, the rinsing time, the drying method, and the like were the same as in the examples, and the conditions that did not generate microbubbles were carried out as comparative examples.
Result: The removal of the wrapping oil residue was evaluated visually and by a photograph. As a result, it was found that there was an effect on the cleaning of microbubbles.

(Example 5) Removal of oil-based ink Sample: Three types of 200 mm diameter silicon wafers were used: wafers immediately after lapping, wafers immediately after etching, and mirror wafers. Oil-based ink (blue) was applied to the wafer surface and dried.

  Cleaning chemical: Castrol No. 200 (0.1-1 wt% -KOH + surfactant (2-5 wt% -polyoxyethylene nonylphenyl ether)) was diluted 20-200 times and used.

  Cleaning method: 4L of chemical solution is put in the cleaning tank, and one nozzle part of the microbubble device (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) is installed at the bottom of the cleaning tank, and 1L / min microbubbles are placed. Generated. Air was used as the bubble gas. Microbubbles were generated for 5 minutes before introducing the wafer into the cleaning tank, and the microbubbles continued to be generated during cleaning.

The sample was immersed here at a liquid temperature of 20 ° C. for 5 minutes. After the sample was taken out, it was placed in a 20 ° C. ultrapure water bath and rinsed for 10 minutes. Thereafter, the sample was dried by blowing dry air.
The chemical solution tank, the chemical solution composition, the chemical solution amount, the washing time, the rinsing time, the drying method, and the like were the same as in the examples, and the conditions that did not generate microbubbles were carried out as comparative examples.

  Result: The degree of oil-based ink removal was evaluated visually and by photographs. The results are shown in Table 2. It has been found that it has an effect on the cleaning of microbubbles. In particular, a mirror wafer with a smooth surface state can be removed even under conditions without microbubbles, but a wafer with a relatively rough surface state immediately after lapping processing and a wafer immediately after etching processing cannot be sufficiently removed without microbubbles. It has been found that a significant cleaning effect appears by using bubbles.

Table 2 shows that oil-based ink removal is significantly improved by the presence of microbubbles.
Example 6 Silicon Wafer Etching Rate in Cleaning Sample: An evaluation sample was prepared by depositing a polysilicon layer with a thickness of about 1 μm by CVD on a mirror surface of a 200 mm diameter silicon wafer.

  Measurement: The thickness of the polysilicon layer before and after the cleaning treatment was measured with an ellipsometer.

  Cleaning fluid: Castrol No. 200 (0.1-1 wt% -KOH + surfactant (2-5 wt% -polyoxyethylene nonylphenyl ether)) was diluted 20-200 times and used.

Cleaning method: Put 80 L of chemical in the cleaning tank, and provide one micro bubble device (M2-MS / PTFE type manufactured by Nano Planet Research Laboratories) at the bottom of the cleaning tank. Generated. The sample was immersed in it at 50 ° C. for 12 minutes. In the example in which ultrasonic treatment was applied, the conditions of a frequency of 28 kHz and an output of 1 kW were used. After the sample was taken out, it was placed in a 20 ° C. ultrapure water bath and rinsed for 10 minutes. Thereafter, the sample was dried by blowing dry air.
The chemical tank, chemical composition, chemical amount, cleaning time, rinse time, drying method, etc. are the same as in the examples,
(1) No ultrasound, no microbubbles,
(2) Ultrasound, no microbubbles,
(3) Without ultrasonic waves, with microbubbles,
(4) The test was performed under four conditions with ultrasonic waves and microbubbles.

  Result: The thickness of the polysilicon layer before and after the cleaning treatment was measured with an ellipsometer to obtain the etching rate. The results are shown in FIG.

  From FIG. 3, it can be seen that the presence of microbubbles can improve the etching rate during the cleaning process. As a result, the ability to remove various contaminants (particles, ions, metals, organic substances, etc.) on the wafer surface can be expected.

  The silicon wafer wet processing method according to the present invention is a completely new method and can be applied to all conventional silicon wafer wet processing. In particular, the method according to the present invention includes a cleaning process after slicing, a particle removing and cleaning process using APM, a particle removing and cleaning process using a cleaning liquid containing hydrogen water, a residue cleaning process after a lapping process, an oily ink removing and cleaning process, Or, it has an excellent effect in a cleaning process involving etching.

FIG. 1 is a diagram showing the results of Example 2. FIG. 2 is a diagram showing the results of Example 3. FIG. 3 is a diagram showing the results of Example 6.

Claims (7)

  A method for wet-treating a silicon wafer, characterized in that the method is performed in the presence of microbubbles.   The silicon wafer wet processing method according to claim 1, wherein the wet processing is post-slicing cleaning processing.   The wet processing method for a silicon wafer according to claim 1, wherein the wet processing is a particle removal cleaning process using APM (ammonia + hydrogen peroxide) of the silicon wafer.   The silicon wafer wet processing method according to claim 1, wherein the wet processing is particle removal cleaning processing using a cleaning liquid containing hydrogen water.   The silicon wafer wet processing method according to claim 1, wherein the wet processing is a residue removal cleaning process after the lapping process.   The silicon wafer wet processing method according to claim 1, wherein the wet processing is oil-based ink removal cleaning processing.   The silicon wafer wet processing method according to claim 1, wherein the wet processing is a cleaning process involving etching of silicon.

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