Wafer exposure method

Abstract

The invention discloses a wafer exposure method, which mainly adopts an exposure machine to expose a wafer according to the wafer exposure method, and the wafer is positioned on a bearing table of a wafer bearing table during exposure. The wafer exposure method comprises the following steps: writing a preset subprogram into an executive program of an exposure machine; calling the subprogram to expose the wafer on the wafer bearing table within first time after the exposure machine is shut down and restarted; and after the exposure reaches the first time, exiting the subprogram, and continuing to expose the subsequent wafer by adopting the execution program. In the first time, the temperature of the wafer bearing table is gradually reduced to a stable value, and the subprogram comprises a mapping relation between the exposure time and the amplification factor compensation amount. The subprogram is called in the first time when the temperature of the wafer bearing table changes to provide the amplification factor compensation amount so as to compensate the overlay error caused by expansion of the wafer, a blocking control wafer is not needed, the utilization rate of a machine table is improved, and the cost is saved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and particularly to a method for exposing a wafer. Background Art

[0002] A projection exposure apparatus can project circuit patterns on a mask onto a substrate coated with a photosensitive resin through an optical system such as a projection objective lens at a certain magnification or reduction ratio. Currently, projection exposure apparatuses have been widely used in the manufacturing of integrated circuits, and in recent years, the application scope has been extended to fields such as flat panel display and printed circuit board manufacturing.

[0003] Figure 1 The schematic diagrams of a wafer exposure apparatus and a wafer exposure method of the prior art are shown. As Figure 1 shown, a wafer stage 203 is used to carry a wafer. A wafer chuck (water table) 202 is formed on the surface of the wafer stage 203, and the wafer 201 can be placed on the wafer chuck 202 to receive exposure. An exposure machine 100 is used to expose the wafer 201. In the exposure process of a traditional exposure machine, during the working stage, each wafer 201 on the wafer chuck 202 is exposed in sequence. The temperature on the wafer chuck 202 is basically constant, and the wafer 201 does not expand. During the working process, for example, 25 wafers can be exposed in sequence at one time, and then it enters the shutdown stage. During the shutdown process, the exposure machine 100 moves away from the wafer chuck 202, and the wafer chuck 202 is not in contact with water, resulting in a gradual increase in the temperature on the surface of the wafer chuck 202 and then reaching a saturation value. Then, when the wafer needs to be exposed again next time, the high temperature on the wafer chuck 202 will cause the first wafer to expand, and the amount of expansion is relatively large. After the first wafer is exposed, the temperature on the wafer chuck 202 also gradually drops to a stable value. Therefore, a large overlay error will be formed between the first wafer and the subsequent wafers.

[0004] In order to improve the overlay error, in the existing exposure machine 100, after restarting and entering the working stage, a dummy wafer or a monitor wafer stored in the exposure machine 100 will be automatically placed on the wafer chuck 202 to replace the first wafer for exposure operation. Then, after the temperature drops to a stable value, the actual first wafer is placed on the wafer chuck 202 for exposure. This is used to reduce the overlay abnormality of the first wafer caused by temperature difference. However, this approach will increase the usage amount of dummy wafers and reduce the machine utilization rate, increasing the cost. Summary of the Invention

[0005] In order to solve the above technical problems, the present application provides a method for exposing a wafer.

[0006] According to one aspect of the present invention, there is provided a wafer exposure method. An exposure machine is used to expose a wafer according to the wafer exposure method. When exposing, the wafer is located on the wafer stage of the wafer carrier. The wafer exposure method includes: writing a preset subroutine into the execution program of the exposure machine; calling the subroutine to expose the wafer on the wafer stage within the first time after the exposure machine is restarted after shutdown; exiting the subroutine after the exposure reaches the first time, and using the execution program to continue exposing subsequent wafers. Wherein, within the first time, the temperature of the wafer stage gradually decreases to a stable value, and the subroutine includes the mapping relationship between the exposure time and the magnification compensation amount.

[0007] Optionally, within the first time, as the exposure time increases, the magnification compensation amount decreases.

[0008] Optionally, within the first time, the magnification compensation amount has a positive correlation with the expansion amount of the wafer due to heat.

[0009] Optionally, within the first time, the first wafer on the wafer stage is exposed, and after the first time, the second wafer and subsequent wafers on the wafer stage are exposed.

[0010] Optionally, within the first time, the magnification compensation amount decreases from the maximum value to zero, and the magnification during wafer exposure within the first time is the sum of the initial magnification and the magnification compensation amount, and the magnification during wafer exposure after the first time is the initial magnification.

[0011] Optionally, the wafer exposure method further includes: obtaining the first time; obtaining the variation relationship between the expansion amount of the wafer due to heat and the exposure time within the first time to obtain the mapping relationship between the exposure time and the magnification compensation amount; writing a subroutine according to the first time and the mapping relationship.

[0012] Optionally, the step of obtaining the first time includes: detecting the temperature change of the wafer stage after the exposure machine is restarted after shutdown; recording the time when the temperature of the wafer stage decreases from the maximum value to the stable value multiple times; obtaining the first time according to the multiple times.

[0013] Optionally, the step of obtaining the relationship between the expansion amount of the wafer due to heat and the exposure time within the first period of time, and obtaining the mapping relationship between the exposure time and the magnification compensation amount includes: sampling at the same time interval multiple times within the first period of time to obtain the expansion amount of the wafer, predicting the corresponding magnification compensation amount; establishing the relationship between the expansion amount and the magnification compensation amount varying with the exposure time; verifying and correcting the relationship between the expansion amount and the magnification compensation amount varying with the exposure time multiple times to obtain the mapping relationship between the exposure time and the magnification compensation amount.

[0014] Optionally, the wafer exposure method further includes: regularly updating the subroutine and rewriting it into the execution program of the exposure machine.

[0015] Optionally, the wafer exposure method further includes: detecting the overlay error of the wafer after exposure and using it as a reference factor to update the subroutine.

[0016] The wafer exposure method provided by the present invention first forms a subroutine according to the relationship between the expansion amount of the wafer, the magnification compensation amount, and the first period of time of temperature drop, and writes it into the execution program of the exposure machine. After the exposure machine is shut down and restarted, the machine is hung with the subroutine to expose the wafer. Thus, the magnification of the first wafer is compensated according to the magnification compensation amount in the subroutine, so that the overlay error caused by the expansion amount of the wafer due to heat can be compensated by the magnification compensation amount. Furthermore, it is possible to ensure the overlay accuracy without using a reticle, improve the compensation method of the exposure machine, effectively reduce the usage amount of reticles, and increase the utilization rate of the machine, significantly reducing costs.

[0017] It should be noted that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. Description of the Drawings

[0018] Figure 1 Shows a schematic diagram of a wafer exposure apparatus and a wafer exposure method in the prior art;

[0019] Figure 2 Shows a schematic flowchart of a wafer exposure method according to an embodiment of the present invention;

[0020] Figure 3 Shows a schematic diagram of the relationship between the magnification compensation amount, the wafer expansion amount, and the exposure time in the wafer exposure method according to an embodiment of the present invention;

[0021] Figure 4 Shows a working schematic diagram of an exposure machine implementing the wafer exposure method according to an embodiment of the present invention. Detailed Embodiments

[0022] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0023] Figure 2 A schematic flow chart of a wafer exposure method according to an embodiment of the present invention is shown.

[0024] As Figure 2 shown, the wafer exposure method of this embodiment is applicable in an exposure machine. For example, the exposure machine 100 shown in Figure 1 exposes the wafer 201 according to the wafer exposure method. When exposing, the wafer 201 is located on the wafer stage 202 of the wafer stage 203. The wafer exposure method of this embodiment includes the following steps.

[0025] In step S101, a preset subroutine is written into the execution program of the exposure machine.

[0026] In this step, first, the preset subroutine is obtained, and then the subroutine is written into the execution program of the exposure machine 100. The execution program is, for example, the main program, and the subroutine is added at the end or other positions of the main program. When the main program is executed and the subroutine is called, the subroutine is executed first, and after exiting the subroutine, the main program continues to be executed. The subroutine may include the mapping relationship between the exposure time and the magnification compensation amount.

[0027] In step S102, the subroutine is called within the first time after the exposure machine stops and restarts to expose the wafer on the wafer stage.

[0028] In this step, when the exposure machine stops and restarts and enters the working stage again, the exposure machine 100 calls the subroutine to compensate the magnification according to the relationship between the exposure time and the magnification compensation amount, and exposes the wafer 201 according to the compensated magnification within the first time, so that the compensated pattern can match the expanded wafer. The temperature of the wafer stage 202 gradually decreases from the maximum value to the stable value within the first time. During this period, the wafer 201 on the wafer stage 202 will expand due to the high temperature. At this time, the magnification is compensated, and after the compensation, the exposure is carried out to avoid registration errors.

[0029] In step S103, after the exposure reaches the first time, the subroutine is exited, and the execution program is used to continue exposing the subsequent wafers.

[0030] In this step, after the exposure reaches the first time, since the temperature on the wafer stage 202 is stable, there is no need to compensate for the magnification at this time. Therefore, the subroutine can be exited and the main program can be continued to expose the wafer using the initial magnification.

[0031] Figure 3 The schematic diagram showing the relationship among the magnification compensation amount, the wafer expansion amount, and the exposure time in the wafer exposure method according to an embodiment of the present invention is shown.

[0032] As Figure 3 shown, within the first time, the temperature on the wafer stage 202 gradually decreases from the maximum value to the stable value, the expansion amount of the wafer also gradually decreases with the exposure time, and the required compensation amount is smaller. Therefore, within this time, the magnification compensation amount is positively correlated with the expansion amount of the wafer caused by heat, that is, the magnification compensation amount decreases as the exposure time increases. Within this first time, the magnification compensation amount decreases from the maximum value to zero, and the magnification during wafer exposure within the first time is the sum of the initial magnification and the magnification compensation amount, and the magnification during wafer exposure after the first time is the initial magnification.

[0033] Further, within the first time, only the first wafer on the wafer stage is exposed, and within the time after the first time, the second wafer and subsequent wafers on the wafer stage are exposed. That is, generally after the first wafer is exposed, the temperature on the wafer stage 202 will gradually decrease to the stable value, and at this time, the magnification compensation amount can be reduced to zero. After that, starting from the second wafer, the exposure can be performed according to the initial magnification.

[0034] Further, after performing step S101, the wafer exposure method of this embodiment may further include: obtaining the first time; obtaining the variation relationship of the expansion amount of the wafer caused by heat with the exposure time within the first time to obtain the mapping relationship between the exposure time and the magnification compensation amount; and writing a subroutine according to the first time and the mapping relationship. That is, how to obtain the subroutine and the corresponding mapping relationship.

[0035] Specifically, the step of obtaining the first time may include: detecting the temperature change of the wafer stage after the exposure machine is restarted after shutdown; recording the time when the temperature of the wafer stage decreases from the maximum value to the stable value multiple times; and obtaining the first time according to the multiple times. That is, recording the time period during which the temperature of the wafer stage drops after the exposure machine is restarted after shutdown multiple times, and obtaining the first time according to the multiple time periods. For example, taking the average value of multiple results, etc.

[0036] The steps of obtaining the relationship between the expansion amount of the wafer due to heat and the exposure time within the first period of time, and obtaining the mapping relationship between the exposure time and the magnification compensation amount may include: sampling at the same time interval multiple times within the first period of time to obtain the expansion amount of the wafer, and predicting the corresponding magnification compensation amount; establishing the relationship between the expansion amount and the magnification compensation amount changing with the exposure time; verifying and correcting the relationship between the expansion amount and the magnification compensation amount changing with the exposure time multiple times to obtain the mapping relationship between the exposure time and the magnification compensation amount. That is, predicting the magnification compensation amount based on the expansion amount of the wafer within the first period of time, and then verifying and correcting the magnification compensation amount through multiple wafer exposure experiments to obtain the most suitable result. Then, a subroutine is written according to the mapping relationship between the magnification compensation amount and the exposure time. Multiple moments can be taken within the first period of time, and each moment corresponds to a magnification compensation amount, so that a one-to-one mapping relationship can be obtained. That is, within the entire first period of time, the magnification compensation amount can change with the exposure time.

[0037] Further, after sequentially exposing multiple wafers (for example, 25 wafers), the wafer exposure method of this embodiment may further include: regularly updating the subroutine and rewriting it into the execution program of the exposure machine. The relationship between the magnification compensation amount and the wafer expansion amount can be regularly checked, and then the subroutine is updated and rewritten regularly to ensure the minimum overlay error. Of course, the wafer exposure method may further include: detecting the overlay error of the wafer after exposure and using it as a reference factor to update the subroutine. That is, the overlay error can be detected after each exposure and used as a reference factor to continuously update and correct the subroutine, so that the magnification compensation amount is closer and closer to the actual requirement.

[0038] Figure 4 The working schematic diagram of an exposure machine for implementing the wafer exposure method of the embodiment of the present invention is shown.

[0039] As Figure 4 shown, according to the above wafer exposure method, in the working stage outside the first period of time, the wafer is exposed using the initial magnification. In the shutdown stage, the temperature on the susceptor 202 gradually rises to the saturation value, that is, the maximum value. Then, in the working stage after the exposure machine is restarted after shutdown, the subroutine is executed within the first period of time to compensate the magnification of the first wafer so that the compensation amount can match the expansion amount. Then, after the first period of time, the second wafer and subsequent wafers are exposed using the initial magnification. After the first wafer cools and recovers, the overlay error between it and the subsequent second wafer is very small. Therefore, the wafer exposure method of this embodiment does not need to use a dummy wafer, which can save raw materials. Moreover, the first wafer can be directly exposed, ensuring the overlay accuracy while improving the machine utilization efficiency and saving a large amount of costs.

[0040] In summary, for the wafer exposure method provided by the present invention, a subroutine is first formed according to the relationship between the expansion amount of the wafer, the magnification compensation amount, and the first time of temperature drop, and written into the execution program of the exposure machine. After the exposure machine is restarted after shutdown, the machine is hung with the subroutine to expose the wafer. Thus, the magnification of the first wafer is compensated according to the magnification compensation amount in the subroutine, so that the overlay error caused by the expansion amount of the wafer due to heat can be compensated by the magnification compensation amount. Furthermore, it is possible to ensure the overlay accuracy without using a reticle control wafer, improve the compensation method of the exposure machine, effectively reduce the usage amount of the reticle control wafer, and increase the machine utilization rate, significantly reducing the cost.

[0041] Finally, it should be noted that: Obviously, the above embodiments are merely examples for clearly illustrating the present invention and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

[0042] It should also be understood that the terms and expressions used herein are only for description, and one or more embodiments of this specification should not be limited to these terms and expressions. Using these terms and expressions does not mean excluding any equivalent features of the illustration and description (or parts thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, changes, and substitutions may also exist. Accordingly, the claims should be regarded as covering all such equivalents.

Claims

1. A wafer exposure method, comprising: Writing a preset subroutine into the execution program of an exposure machine; Invoking the subroutine to expose the wafer on a susceptor within the first period of time after the exposure machine is restarted after shutdown; Exiting the subroutine after the exposure reaches the first period of time, and continuing to expose subsequent wafers using the execution program, wherein, within the first period of time, the temperature of the susceptor gradually decreases to a stable value, and the subroutine includes a mapping relationship between exposure time and magnification compensation amount.

2. The wafer exposure method according to claim 1, wherein, Within the first period of time, the magnification compensation amount decreases as the exposure time increases.

3. The wafer exposure method according to claim 2, wherein, Within the first period of time, the magnification compensation amount is positively correlated with the expansion amount of the wafer due to heat.

4. The wafer exposure method according to claim 2, wherein, Within the first period of time, the first wafer on the susceptor is exposed, and after the first period of time, the second wafer and subsequent wafers on the susceptor are exposed.

5. The wafer exposure method according to claim 2, wherein, Within the first period of time, the magnification compensation amount decreases from the maximum value to zero, and the magnification during wafer exposure within the first period of time is the sum of the initial magnification and the magnification compensation amount, and the magnification during wafer exposure after the first period of time is the initial magnification.

6. The wafer exposure method according to claim 1, further comprising: Obtaining the first period of time; Obtaining the variation relationship of the expansion amount of the wafer due to heat with the exposure time within the first period of time, and obtaining the mapping relationship between the exposure time and the magnification compensation amount; Writing the subroutine according to the first period of time and the mapping relationship.

7. The wafer exposure method according to claim 6, wherein The step of obtaining the first period of time includes: Detecting the temperature change of the susceptor after the exposure machine is restarted after shutdown; Recording the time when the temperature of the susceptor decreases from the maximum value to the stable value multiple times; Obtaining the first period of time based on the multiple times.

8. The wafer exposure method according to claim 6, wherein, The step of obtaining the variation relationship of the expansion amount of the wafer due to heat with the exposure time within the first period of time, and obtaining the mapping relationship between the exposure time and the magnification compensation amount includes: Sampling at the same time interval multiple times within the first period of time to obtain the expansion amount of the wafer, and predicting the corresponding magnification compensation amount; Establishing the relationship between the expansion amount and the magnification compensation amount varying with the exposure time; Verifying and correcting the relationship between the expansion amount and the magnification compensation amount varying with the exposure time multiple times to obtain the mapping relationship between the exposure time and the magnification compensation amount.

9. The wafer exposure method according to claim 1, further comprising: Regularly updating the subroutine and rewriting it into the execution program of the exposure machine.

10. The wafer exposure method according to claim 1, wherein, Further comprising: Detecting the overlay error of the wafer after exposure, and using it as a reference factor to update the subroutine.

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