JP2007088328A - Method for washing immersion exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an immersion exposure device washing method that makes it possible to easily wash the projection lens of an immersion exposure device. <P>SOLUTION: This method has been devised to wash an immersion exposure device 1 which has a projection lens 4 above a semiconductor substrate 2, and contains an immersion liquid 5 between the semiconductor substrate 2 and the projection lens 4. The semiconductor substrate 2 with a cleaning agent 12 applied is covered with the immersion liquid 5, and then the projection lens 4 is run on that semiconductor 2. In this way, the cleaning agent 12 is resolved into the immersion liquid 5, so that the immersion exposure device 1 can be washed without removing the projection lens 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cleaning method for an immersion type exposure apparatus.

  An immersion type exposure apparatus is an apparatus that fills at least a part between the lower surface of a projection lens and a substrate surface with an immersion liquid and transfers an image of a mask pattern onto the substrate via the immersion liquid. This immersion type exposure apparatus can increase the resolution by using an immersion liquid with n> 1 by utilizing the fact that the wavelength of exposure light in the immersion liquid is 1 / n that of air. In recent years, as the performance of semiconductor devices has been improved, the size of the semiconductor device has been remarkably reduced, and the immersion type exposure apparatus is currently attracting attention in order to further reduce the size.

  Conventionally, since the immersion type exposure apparatus fills the immersion liquid between the lower surface of the projection lens and the substrate surface, the resist on the substrate surface dissolves into the immersion liquid during the operation of the immersion type exposure apparatus. There is a problem that the surface of the projection lens in contact with the immersion liquid is contaminated. This contamination of the projection lens decreases the intensity of the exposure light irradiated on the substrate surface, and the exposure cannot be performed with high accuracy.

Therefore, as one of the projection lens cleaning methods for solving this problem, for example, there is a method of removing the immersion liquid of the immersion exposure apparatus and cleaning the projection lens directly using a cleaning liquid and a brush ( For example, see Patent Document 1.) However, in this cleaning method, complicated steps must be taken, and the projection lens must be cleaned using various cleaning devices.
Japanese Patent Laying-Open No. 2005-72404 (page 8, FIG. 1)

  It is an object of the present invention to provide a cleaning method for an immersion type exposure apparatus that can easily clean the projection lens of the immersion type exposure apparatus.

  According to another aspect of the present invention, there is provided a semiconductor device having a projection lens above a semiconductor substrate, and a cleaning agent in a cleaning method for an immersion type exposure apparatus in which an immersion liquid is filled between the semiconductor substrate and the projection lens. And a step of filling the immersion liquid onto the semiconductor substrate coated with the liquid and a step of scanning the projection lens over the semiconductor substrate, wherein the cleaning agent dissolves into the immersion liquid. .

  According to the present invention, the projection lens of the immersion type exposure apparatus can be easily cleaned.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of an immersion type exposure apparatus in which the immersion type exposure apparatus is simplified to show a cleaning method for an immersion type exposure apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, an immersion type exposure apparatus 1 includes a wafer stage 3 on which a semiconductor wafer 2 is placed and a projection lens 4 that is positioned above the wafer stage 3 and that irradiates the semiconductor wafer 2 with exposure light. It has. An immersion liquid 5 is filled between the projection lens 4 and the wafer stage 3, and the projection lens 4 and the wafer stage 3 are passed from the right side of the projection lens 4 through the nozzle 7 by the immersion supply device 6. In the meantime, the immersion liquid 5 is supplied. Then, the immersion liquid 5 between the projection lens 4 and the wafer stage 3 is discharged through the nozzle 9 by the immersion discharge device 8 on the left side of the projection lens 4. The immersion liquid 5 between the projection lens 4 and the wafer stage 3 is discharged simultaneously with the supply.

  A reticle for transferring a mask pattern to the semiconductor wafer 2 is provided above the projection lens 4, and the mask pattern is transferred onto the semiconductor wafer 2 by irradiating the reticle with exposure light.

  In Embodiment 1 of the present invention, a cleaning liquid 12 is applied on the semiconductor wafer 2 in order to clean the projection lens 4 of the immersion type exposure apparatus 1. Here, an acidic aqueous solution or a basic aqueous solution can be used as the cleaning liquid 12. For example, hydrofluoric acid, ammonium fluoride, sulfuric acid, hydrogen peroxide, or the like can be used as the acidic aqueous solution. Further, as the basic aqueous solution, an alkaline aqueous solution such as ammonium hydroxide, an organic alkaline aqueous solution such as tetramethylammonium hydride, or the like can be used. Also, the concentration of the cleaning liquid can be changed variously.

  A cleaning method of the immersion type exposure apparatus 1 configured as described above will be described with reference to FIG. FIG. 2 is a flowchart showing a series of steps showing the cleaning method of the immersion type exposure apparatus 1 according to the first embodiment of the present invention.

  First, a cleaning agent 12 necessary for cleaning the projection lens 4 of the immersion type exposure apparatus 1 of the present embodiment is applied on the semiconductor wafer 2 (S101). Here, the cleaning agent 12 can be spin-coated on the semiconductor wafer 2 using, for example, a coating processing apparatus such as a spin coater. Moreover, as the cleaning agent 12, an acidic aqueous solution or a basic aqueous solution as described above can be used.

  Next, the semiconductor wafer 2 coated with the cleaning agent 12 is transported onto the wafer stage 3 of the immersion type exposure apparatus 1, and the semiconductor wafer 2 is placed on the wafer stage 3 below the projection lens 4 (S102).

  Next, the exposure operation of the immersion type exposure apparatus 1 is started (S103). First, the immersion liquid 5 is supplied between the projection lens 4 and the semiconductor wafer 2 by the immersion liquid supply device (S104). At this time, the cleaning liquid on the semiconductor wafer 2 is dissolved into the immersion liquid 5 by the supply of the immersion liquid 5. The projection lens 4 of the immersion type exposure apparatus 1 is cleaned by the cleaning liquid dissolved in the immersion liquid 5. Further, the supplied immersion liquid 5 is discharged in parallel with the supply operation, and the immersion liquid 5 is circulated.

  Next, the semiconductor wafer 2 is exposed as when the mask pattern is transferred onto the semiconductor wafer 2 (S105). At this time, the projection lens 4 is not irradiated with exposure light, but is subjected to pseudo exposure, and the entire semiconductor wafer 2 is scanned by the immersion type exposure apparatus 1. As a result, the semiconductor wafer 2 coated with the cleaning agent 12 can be scanned by the immersion type exposure apparatus 1, and the projection lens 4 is always cleaned with the immersion liquid 5 from which the cleaning agent 12 has dissolved. It becomes possible.

  Thus, the exposure operation ends (S106). At this time, when the projection lens 4 is further cleaned using the semiconductor wafer 2 coated with another cleaning agent 12, the projection is performed using another cleaning liquid by performing the steps S101 to S106 described above. The lens 4 can be washed. Here, when the projection lens 4 is cleaned again using another cleaning liquid, the cleaning liquid used first may be used as it is, or the same type of cleaning liquid whose concentration is changed may be used. Different types of cleaning liquids can also be used at various concentrations.

  Here, in the exposure of the present embodiment, the entire semiconductor wafer 2 is scanned without irradiating the projection lens 4 with the exposure light. However, the exposure may be performed while irradiating the exposure light. In that case, contaminants attached to the projection lens can be more effectively removed by the high optical energy of the irradiated exposure light, and the cleaning effect of the projection lens can be improved.

  Furthermore, after supplying the immersion liquid between the projection lens and the semiconductor substrate, the projection lens was scanned on the semiconductor substrate as an exposure process, but even if the projection lens is not scanned, the cleaning liquid on the semiconductor substrate is By supplying the immersion liquid, the projection lens can be cleaned by dissolving in the immersion liquid.

  As described above, since the projection lens can be cleaned without removing the projection lens from the immersion exposure apparatus, the projection lens of the immersion exposure apparatus can be cleaned more easily than in the past. Therefore, since the projection lens of the immersion exposure apparatus can be efficiently cleaned, it is possible to prevent a decrease in lens transmittance and unevenness due to contamination of the projection lens. Furthermore, in this embodiment, the cleaning agent dissolved in the immersion liquid can clean not only the projection lens but also the nozzle that supplies and discharges the immersion liquid in the immersion liquid.

  FIG. 3 is a flowchart showing a series of steps showing a cleaning method for an immersion type exposure apparatus according to Embodiment 2 of the present invention. A cleaning method for the immersion type exposure apparatus according to the second embodiment of the present invention shown in FIG. 3 will be described with reference to FIG.

  The present embodiment is a more specific embodiment of the first embodiment. That is, in this embodiment, the projection lens 4 is cleaned using the semiconductor wafer 2 coated with an acidic aqueous solution and a basic aqueous solution, which are a plurality of cleaning agents 12.

  First, an acidic aqueous solution that is a cleaning agent 12 necessary for cleaning the projection lens 4 is applied on the semiconductor wafer 2 (S201).

  Next, as in Example 1, the semiconductor wafer 2 coated with the acidic aqueous solution 12 is transferred onto the wafer stage 3 of the immersion type exposure apparatus 1 (S202), and an exposure operation is started (S203).

  In this exposure operation, as in the first embodiment, the immersion liquid 5 is supplied (S204), followed by exposure (S205), and the exposure operation ends (S206). At this time, in the supply of the immersion liquid 5, the acidic aqueous solution 12 applied on the semiconductor wafer 2 is dissolved in the immersion liquid 5, and the dirt attached to the projection lens 4 can be washed. Then, while supplying the immersion liquid 5, exposure is performed in S <b> 205, and the entire semiconductor wafer 2 is scanned, so that the acidic aqueous solution 12 on the semiconductor wafer is dissolved into the immersion liquid 5 as needed, and the projection lens 4. Cleaning can be performed.

  When the exposure operation is completed in S206 and the projection lens 4 is cleaned with another acidic aqueous solution 12, the process returns to S201, and steps S201 to S206 may be performed. When the next cleaning of the projection lens 4 with the basic aqueous solution 12 is not necessary, the cleaning process of the projection lens 4 is finished as it is.

  Next, when the projection lens 4 is cleaned with the acidic aqueous solution 12, the projection lens 4 is subsequently cleaned with the basic aqueous solution 12. First, as in Example 1, the basic aqueous solution 12 is applied on the semiconductor wafer 2 (S207).

  Next, similarly to the semiconductor wafer 2 to which the acidic aqueous solution 12 is applied, the semiconductor wafer 2 is transported (S208), and an exposure operation is started (S209). Then, similarly to the acidic aqueous solution 12 described above, the immersion liquid 5 is supplied (S210), exposure is performed (S211), and the exposure operation ends (S212). At this time, similar to the acidic aqueous solution 12, the basic aqueous solution 12 applied onto the semiconductor wafer 2 can also be dissolved into the immersion liquid 5 and the dirt adhering to the projection lens 4 can be washed. Then, while supplying the immersion liquid 5, exposure is performed in S <b> 211, and the entire semiconductor wafer 2 is scanned, so that the aqueous base solution on the semiconductor wafer is dissolved in the immersion liquid 5 as needed, and the projection lens 4 is cleaned. It can be performed.

  When the exposure operation is completed in S212 and the projection lens 4 is cleaned with the next basic aqueous solution 12, the process returns to S207, and steps S207 to S212 may be performed. If it is desired to clean the projection lens 4 again with the acidic aqueous solution 12, the process returns to S201, and steps S201 to S206 may be performed. When the cleaning of the projection lens 4 with all of the acidic aqueous solution 12 and the basic aqueous solution 12 is completed, the entire process is completed.

  Here, as the acidic aqueous solution and the basic aqueous solution used for the cleaning agent 12, for example, hydrofluoric acid, ammonium fluoride, sulfuric acid, hydrogen peroxide, and the like can be used for the acidic aqueous solution 12. An aqueous alkali solution such as ammonium hydroxide or an organic alkaline aqueous solution such as tetramethylammonium hydride can be used. Moreover, it is not necessary to use only the same kind of these acidic aqueous solutions and basic aqueous solutions, and different types of acidic aqueous solutions and basic aqueous solutions can be used, and the projection lens can be cleaned at various concentrations.

  As described above, since the projection lens can be cleaned without removing the projection lens from the immersion exposure apparatus as in the first embodiment, the projection lens of the immersion exposure apparatus can be cleaned more easily than in the past. . Therefore, since the projection lens of the immersion exposure apparatus can be efficiently cleaned, it is possible to prevent a decrease in lens transmittance and unevenness due to contamination of the projection lens. Further, in this embodiment, the cleaning agent dissolved in the immersion liquid can clean not only the projection lens but also the nozzle that supplies and discharges the immersion liquid in the immersion liquid. Further, in this embodiment, since a plurality of cleaning agents having different pH values of the acidic aqueous solution and the basic aqueous solution are used, the projection lens and the immersion liquid that have become acidic by the acidic aqueous solution can be neutralized by the basic aqueous solution. .

  FIG. 4 is a cross-sectional view of an immersion type exposure apparatus in which the immersion type exposure apparatus is simplified to show a cleaning method for an immersion type exposure apparatus according to Embodiment 3 of the present invention. FIG. 5 is a flowchart showing a series of steps showing a cleaning method for an immersion type exposure apparatus according to Embodiment 3 of the present invention.

  The difference of the present embodiment from the above-described embodiments is that in Embodiment 1 and Embodiment 2, the immersion liquid 5 supplied between the projection lens 4 and the semiconductor wafer 2 is discharged as it is. Then, as shown in FIG. 4, a pH measuring device 13 for measuring the pH value of the immersion liquid 5 discharged from the nozzle 9 is provided. Thereby, the pH value of the immersion liquid 5 after cleaning the projection lens 4 and during cleaning can be known. In addition, about the other same structure as FIG.1 and FIG.2, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  A cleaning method for the immersion type exposure apparatus according to the third embodiment of the present invention shown in FIG. 5 will be described with reference to FIG.

  First, since the operation from the application of the cleaning agent 12 (S101) to the end of the exposure operation (S106) is the same as that in the first embodiment, the description thereof is omitted.

  When the exposure operation is completed, the pH value of the immersion liquid 5 discharged from the immersion type exposure apparatus 1 is measured using the pH measurement apparatus 13 (S107). At this time, when the pH value shows a neutral value, the process is finished as it is. Further, assuming that the pH value is slightly acidic or alkaline, if the immersion liquid 5 is continuously supplied as it is, the process can be similarly completed as long as the value is neutral.

  Next, when the pH value cannot be neutralized only by supplying the immersion liquid 5, the type and concentration of the cleaning agent 12 that can neutralize the immersion liquid according to the pH value. And the steps from S101 to S106 may be performed using the cleaning agent 12. In S107, the pH value is measured again, and the process ends if the above-described conditions are satisfied.

  Here, an acidic aqueous solution or a basic aqueous solution can be used as the cleaning liquid 12. For example, hydrofluoric acid, ammonium fluoride, sulfuric acid, hydrogen peroxide, or the like can be used as the acidic aqueous solution. Further, as the basic aqueous solution, an alkaline aqueous solution such as ammonium hydroxide, an organic alkaline aqueous solution such as tetramethylammonium hydride, or the like can be used.

  As described above, since the projection lens can be cleaned without removing the projection lens from the immersion exposure apparatus as in the first embodiment, the projection lens of the immersion exposure apparatus can be cleaned more easily than in the past. . Therefore, since the projection lens of the immersion exposure apparatus can be efficiently cleaned, it is possible to prevent a decrease in lens transmittance and unevenness due to contamination of the projection lens. Similarly to the first embodiment, not only the projection lens but also the nozzle that supplies and discharges the immersion liquid in the immersion liquid can be cleaned by the cleaning agent dissolved in the immersion liquid. Furthermore, in this embodiment, since the pH value can be measured with a pH measuring device after the projection lens is washed, the cleaning agent necessary for neutralizing the immersion liquid can be easily selected, and appropriate. The immersion liquid can be neutralized.

  FIG. 6 is a flowchart showing a series of steps showing a cleaning method for an immersion type exposure apparatus according to Embodiment 4 of the present invention.

  In this embodiment, the above-described Embodiment 3 is further embodied, and the projection lens 4 is cleaned using the semiconductor wafer 2 coated with the acidic aqueous solution and the basic aqueous solution as the plurality of cleaning agents 12. . That is, the pH value of the immersion liquid 5 is measured after the projection lens 4 is washed with the acidic aqueous solution 12 of Example 2 and after the projection lens 4 is washed with the basic aqueous solution 12.

  Hereinafter, a cleaning method for an immersion type exposure apparatus according to Embodiment 3 of the present invention will be described with reference to FIG.

  First, the projection lens 4 is cleaned using the acidic aqueous solution 12 (S201 to S206). Since the steps from S201 to S206 are the same as those in FIG. 3 of the second embodiment, the same reference numerals are given and description thereof is omitted.

  Next, when the cleaning of the projection lens 4 with the acidic aqueous solution 12 is completed, the pH value of the immersion liquid 5 is measured using the pH measuring device 13 (S213). At this time, when the pH value is neutral, slightly acidic, or alkaline, the cleaning process of the projection lens 4 is finished as it is. Further, when the projection lens 4 is washed with the alkaline or acidic aqueous solution 12 having a pH value again, the process returns to S201 and the processes from S201 to S206 may be performed.

  Next, when the pH value indicates acidity, the type and concentration of the basic aqueous solution 12 that can neutralize the immersion liquid according to the pH value are determined, and the basic aqueous solution 12 is used to adjust the projection lens 4. Cleaning is performed (S207 to S212). Note that the steps from S207 to S212 are the same as those in FIG.

  Next, the pH value of the immersion liquid 5 is measured again using the pH measurement device 13 (S214). At this time, when the pH value is neutral, slightly acidic, or alkaline, the cleaning process of the projection lens 4 is finished as it is. When the projection lens 4 is washed with the acidic aqueous solution 12 or the basic aqueous solution 12 again, the process returns to S207 and steps S207 to S212 may be performed. Moreover, when pH value shows alkalinity, it returns to S201 and can perform the above-mentioned same process.

  Here, when the projection lens 4 is washed again with the acidic aqueous solution 12 or the basic aqueous solution 12, the acidic aqueous solution 12 or the basic aqueous solution 12 that can neutralize the immersion liquid according to the pH value of the immersion liquid 5. After determining the type and density, the projection lens 4 is washed again. That is, it is preferable to determine the type and concentration of the acidic aqueous solution 12 or the basic aqueous solution 12 so that the pH value of the immersion liquid 5 is neutral by washing the projection lens 4 again.

  Here, as the acidic aqueous solution and the basic aqueous solution used for the cleaning agent 12, for example, hydrofluoric acid, ammonium fluoride, sulfuric acid, hydrogen peroxide, and the like can be used for the acidic aqueous solution 12. An aqueous alkali solution such as ammonium hydroxide or an organic alkaline aqueous solution such as tetramethylammonium hydride can be used.

  As described above, since the projection lens can be cleaned without removing the projection lens from the immersion exposure apparatus as in the first embodiment, the projection lens of the immersion exposure apparatus can be cleaned more easily than in the past. . Therefore, since the projection lens of the immersion exposure apparatus can be efficiently cleaned, it is possible to prevent a decrease in lens transmittance and unevenness due to contamination of the projection lens. Similarly to the first embodiment, not only the projection lens but also the nozzle that supplies and discharges the immersion liquid in the immersion liquid can be cleaned by the cleaning agent dissolved in the immersion liquid. Furthermore, since the pH value can be measured with a pH measuring device after the projection lens is cleaned, as in Example 3, the cleaning agent necessary to neutralize the immersion liquid can be selected and appropriately The immersion liquid can be neutralized.

  The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

1 is a cross-sectional view showing a structure of an immersion type exposure apparatus simplified for explaining a cleaning method for an immersion type exposure apparatus according to Embodiment 1 of the present invention. 2 is a flowchart showing a cleaning method for an immersion type exposure apparatus according to Embodiment 1 of the present invention. 9 is a flowchart showing a cleaning method for an immersion type exposure apparatus according to Embodiment 2 of the present invention. Sectional drawing which shows the structure of the immersion type exposure apparatus simplified in order to demonstrate the cleaning method of the immersion type exposure apparatus which concerns on Example 3 of this invention. 9 is a flowchart showing a cleaning method for an immersion type exposure apparatus according to Embodiment 3 of the present invention. 9 is a flowchart showing a cleaning method for an immersion type exposure apparatus according to Embodiment 4 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Immersion type exposure apparatus 2 Semiconductor wafer 3 Wafer stage 4 Projection lens 5 Immersion liquid 6 Immersion supply apparatus 7, 9 Nozzle 8 Immersion discharge apparatus 12 Cleaning agent (acidic aqueous solution, basic aqueous solution)
13 pH measuring device

Claims (7)

In a cleaning method of an immersion type exposure apparatus having a projection lens above a semiconductor substrate and filled with an immersion liquid between the semiconductor substrate and the projection lens,
A step of performing an exposure process on the semiconductor substrate coated with the first cleaning agent;
The method of cleaning an immersion type exposure apparatus, wherein the first cleaning agent is dissolved in the immersion liquid by the step of performing the exposure process. In a cleaning method of an immersion type exposure apparatus having a projection lens above a semiconductor substrate and filled with an immersion liquid between the semiconductor substrate and the projection lens,
Performing an exposure process on the semiconductor substrate coated with the first cleaning agent;
A step of measuring the pH value of the immersion liquid after performing the exposure process;
And the step of performing the exposure process, wherein the first cleaning agent is dissolved in the immersion liquid. 3. The method for cleaning an immersion type exposure apparatus according to claim 1, further comprising a step of performing an exposure process on the semiconductor substrate coated with the second cleaning agent for neutralizing the immersion liquid. Performing an exposure process on a semiconductor substrate coated with a second cleaning agent that neutralizes the immersion liquid;
A step of measuring the pH value of the immersion liquid after performing the exposure process;
The cleaning method for an immersion type exposure apparatus according to claim 1, further comprising: 5. The cleaning of an immersion type exposure apparatus according to claim 1, wherein the first cleaning agent and the second cleaning agent are an acidic aqueous solution or a basic aqueous solution. Method. 6. The method of cleaning an immersion type exposure apparatus according to claim 5, wherein at least one of hydrofluoric acid, ammonium fluoride, sulfuric acid, and hydrogen peroxide is used as the acidic aqueous solution. 6. The method of cleaning an immersion type exposure apparatus according to claim 5, wherein at least one of ammonium hydroxide and tetramethylammonium hydride is used as the basic aqueous solution.

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