JP2000208411A - Exposure device and exposure method wherein it is used - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a line width of a photoresist pattern uniform regardless of a thickness of a lower film by adjusting an exposure amount by an analyzed reflection light distribution map by a reflection light analyzer wherein a reflection light distribution map can be obtained by analyzing reflection light emitted from a reflection light detector. SOLUTION: The device has a reflection light detector 13 which can detect reflection light (b) which is formed by reflection of light cast on a wafer 3 from a lower film formed in a lower part of a photoresist film through a lens 11 and a mask 9 and reflection light detected by the reflection light detector 13 is analyzed by a reflection light analyzer 15. An exposure adjuster 17 which is connected to the reflection light analyzer 15 and adjusts exposure energy by using a shutter 19 by reflection light analyzed by the reflection light analyzer 15 is provided. The shutter 19 is connected to an exposure adjuster 7. Thereby, exposure energy can be adjusted according to reflectance from each section of a wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a semiconductor device and a method of using the same, and more particularly, to an exposure apparatus used in a photographic process of a semiconductor element and an exposure method using the same.

[0002]

2. Description of the Related Art In general, a semiconductor device is manufactured by repeating a thin film forming process, a diffusion process, an ion implantation process, a photographing process and an etching process. The thin film forming step is a step of forming a thin film on the wafer, the diffusion step is a step of diffusing impurity ions implanted into the wafer surface into the inside of the wafer, and the ion implanting step is a step of implanting impurity ions into the wafer surface. It is a process. Then, the photographic process is a process of selectively irradiating the photoresist film with light using an exposure device and a mask on the wafer on which the photoresist film is formed, and developing the photoresist film to form a fine photoresist pattern on the wafer. The etching process is a process of etching a lower film using the fine photoresist pattern.

Among these, the exposure apparatus used in the photographic process is required to make the line width of the photoresist pattern narrower due to the higher integration of semiconductor elements, and the importance thereof is increasing day by day. . Factors that determine the photoresist pattern line width include the exposure energy of the exposure apparatus.
(Exposure amount), the distance between the wafer and the lens at the time of exposure, the mask line width, the aperture ratio of the lens, the thickness of the lower film formed below the photoresist film, the thickness of the photoresist film, and the like.

[0004]

Among these factors, all factors except the thickness of the lower film are caused by a photographic process using an exposure apparatus, and are considered to be constants with almost no change. However, since the thickness of the lower film depends on the thin film forming process without depending on the photographic process, the thickness of the lower film has a large deviation within a wafer and for each wafer. As a result, even if a photographic process is performed under the same exposure apparatus and exposure conditions, the thickness of the lower film formed under the photoresist film is different, so that the line width of the photoresist pattern cannot be made uniform.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure apparatus which can make the line width of a photoresist pattern uniform regardless of the thickness of a lower film. Another object of the present invention is to provide an exposure method using the exposure apparatus.

[0006]

According to the present invention, there is provided an exposure apparatus comprising: a support for moving a wafer on which a photoresist film is formed in X and Y axes; a mask for selectively transmitting light to the wafer; And a light transmission unit capable of transmitting the light to the mask. The exposure apparatus of the present invention further includes a reflected light detector capable of detecting reflected light reflected by a lower film formed below the photoresist film, and analyzing reflected light emitted from the reflected light detector to reflect light. The apparatus includes a reflected light analyzer that can obtain a light distribution map, and an exposure controller that adjusts an exposure amount based on the reflected light distribution map analyzed by the reflected light analyzer. The lower film may be formed of a nitride film or a composite film of an oxide film and a nitride film, and the support may be configured to move in the X axis and the Y axis using a motor.

According to the exposure method of the present invention, after a desired mask is provided in an exposure apparatus including a reflected light detector, a test wafer on which a photoresist in a wafer lot is formed is loaded on a support of the exposure apparatus. Including stages. Thereafter, the test wafer is subjected to section exposure on the X axis and the Y axis, and at the time of exposure, light reflected by a lower film formed under the photoresist is detected by a reflected light detector, and thereafter, the reflected light is detected by the reflected light detector. The detected reflected light is analyzed by a reflected light analyzer to obtain a reflected light distribution map of the test wafer. Subsequently, after unloading the test wafer, the first wafer in the wafer lot is loaded on the support. Then, the first wafer is sectioned on the X-axis and the Y-axis while adjusting the exposure amount according to the reflected light distribution map analyzed on the test wafer. Then, after unloading the first wafer, the same exposure as that of the first wafer is performed on the second wafer to the last wafer in the wafer lot. The lower layer may be formed of a nitride layer or a composite layer of an oxide layer and a nitride layer, and the exposure amount may be controlled using an exposure controller and a shutter connected to the reflection light analyzer.

The exposure apparatus and the exposure method according to the present invention detect the light reflected by the lower film and adjust the amount of exposure based on the detected light, thereby allowing the lower film to have a critical dimension.
imension) can be improved.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing an embodiment of an exposure apparatus of the present invention including a reflected light detector. FIG. 2 is a reflected light distribution map analyzed by a reflected light analyzer of the exposure apparatus of FIG. FIG. The exposure apparatus of the present invention includes a support 1 for supporting a wafer 3 on which a photoresist film is formed. The motor 2 moves the support 1 in the X and Y axes. A half mirror 7 capable of reflecting and transmitting the light emitted from the light source 5 is provided above the support base 1.
A mask 9 for selectively transmitting the light reflected by the half mirror 7 is provided below the mask 9, and the light selectively transmitted from the mask 9 is provided below the mask 9 to the wafer 3. A lens 11 for irradiation is provided. In FIG. 1, the half mirror 7 and the lens 11 and the like serve as an optical delivery unit for transmitting light through the mask 9, reference numeral a indicates incident light, and reference numeral b indicates reflected light. Show.

Further, the exposure apparatus of the present invention is located above the half mirror 7 so that the reflected light b, ie, the wafer 3
A reflected light detector 13 that can detect, through the lens 11 and the mask 9, reflected light b in which light applied to the substrate is reflected from a lower film formed below the photoresist film;
A reflected light analyzer 15 that can analyze the reflected light detected by the reflected light detector 13; and a shutter 19 that is coupled to the reflected light analyzer 15 and that uses the reflected light analyzed by the reflected light analyzer 15 to use a shutter 19. And an exposure controller 17 for adjusting the exposure energy. The shutter 19 is an exposure controller 1
7. Thus, when the exposure apparatus of the present invention is used, the exposure energy can be adjusted according to the reflectance from each section of the wafer shown in FIG.

After all, the exposure apparatus of the present invention adjusts the light energy applied to the wafer 3 by the exposure controller 17 in consideration of the light reflectance of the lower film as shown in FIG. Can be implemented. That is, the reflectance shown in FIG.
Exposure is performed by increasing the exposure energy when the reflectivity is 0.6% as compared with the case (1), and the amount of light incident on the photoresist film is made the same. As a result, the line width of the photoresist pattern formed on the wafer can be made uniform regardless of the thickness of the lower film.

FIG. 3 is a view showing a wafer prepared for performing exposure by the exposure apparatus according to the present invention, and FIG. 4 is a view showing the reflectance depending on the thickness of the nitride film 23 in FIG. FIG. 5 is a graph showing critical dimensions depending on the thickness of the nitride film 23 of FIG. Specifically, the wafer applied to the exposure apparatus of the present invention is a silicon substrate 21 as shown in FIG.
A nitride film 23 is formed thereon as a lower film, and a photoresist film 25 is formed on the nitride film 23. When exposure is performed on the wafer prepared as described above, the reflectivity varies depending on the thickness of the nitride film 23 as shown in FIG. 4, and as shown in FIG.
(Represented by a square) changes the critical dimension (represented by a circle). That is, the critical dimension varies variously with a constant relationship depending on the thickness of the lower nitride film 23. Therefore, when the exposure energy (exposure amount) is adjusted by the reflectance shown in FIG. 4 using the exposure apparatus of the present invention shown in FIG. 1, a photoresist pattern can be uniformly obtained on the wafer.

FIG. 6 is a view showing another wafer prepared for performing exposure by the exposure apparatus according to the present invention, and FIG. 7 is a view showing the reflectance depending on the thickness of the oxide film 35 and the nitride film 37 in FIG. FIG. 8 is a diagram showing exposure energy depending on the thickness of the oxide film 35 of FIG. 6 for obtaining an appropriate line width. Specifically, as shown in FIG. 6, a wafer applied to the exposure apparatus of the present invention has a tungsten film 33, an oxide film 35, and a nitride film 37 as lower films on a silicon substrate 31.
Is formed, and a photoresist film 39 is formed on the nitride film 37. In this specific example, the tungsten film 3
3 is formed, but may not be formed. When exposure is performed on the wafer prepared as described above, FIG.
As shown in the figure, the reflectivity differs depending on the thickness of the nitride film 37 and the oxide film 35. For example, when the thickness of the nitride film 37 is 250 ° and the thickness of the oxide film 35 is changed from 1850 ° to 1950 °, the reflectance increases from 0.1 to 0.17. In FIG. 7, reference numerals 70, 72, 74, and 76 indicate the reflectivity when the thickness of the oxide film 35 is 1850, 1900, 1950, and 2000, respectively. Therefore, it is necessary to change the exposure energy according to the reflectance using the exposure apparatus of the present invention. That is, the exposure energy must be changed to obtain an appropriate line width value. For example, when the thickness of the nitride film 37 is 250 °, the reflectance increases as the thickness of the oxide film 35 increases from 1850 ° to 1950 °.
The exposure energy must be increased as shown in FIG. In FIG. 8, reference numeral 82 indicates the exposure energy, and reference numeral 84 indicates the thickness of the oxide film 35.

FIG. 9 is a flowchart for explaining an exposure method using the exposure apparatus of the present invention. First, a desired mask is provided in an exposure apparatus including a reflected light detector (step 100). Then, 25 to 5 on the support of the exposure apparatus
A test wafer in a wafer lot (lot) composed of 0 sheets is loaded (step 102). A lower film is already formed on this wafer, and a photoresist film is applied on the lower film. The lower film is, for example, a nitride film or a composite film of an oxide film and a nitride film. continue,
Using a motor connected to the support, the test wafer is
Exposure is performed 40 to 60 times while sequentially moving to the X axis and the Y axis, and reflected light from each section of the test wafer is detected by a reflected light detector (step 104). Thereafter, the reflected light detected by the reflected light detector is analyzed by a reflected light analyzer to obtain a reflected light distribution map for the reflected light of the test wafer (step 106). Thereafter, the test wafer is unloaded (Step 108). Then, the first wafer in the wafer lot is loaded on the support (step 110). The first wafer has a lower film already formed on the wafer similarly to the test wafer, and a photoresist film is formed on the lower film quality. Thereafter, the first wafer is adjusted using a motor connected to the support table while adjusting an exposure amount using an exposure controller according to a reflected light distribution map analyzed on the test wafer.
While moving sequentially to the X axis and the Y axis, 4
Exposure is performed 0 to 60 times (step 112). After that, by unloading the first wafer, the second wafer to the last wafer are subjected to exposure while adjusting the exposure amount using the reflected light distribution map in the same manner as the first wafer. Exposure of one wafer lot is completed (step 114). In the above description, one wafer lot is exposed.However, when many wafer lots are exposed at a manufacturing plant, an arbitrary wafer is selected from each wafer lot to analyze a reflection light distribution map and sometimes fine calibration. This can also be applied to the entire wafer lot while calibrating.

Although the present invention has been described in detail with reference to the embodiment, the present invention is not limited to the above, and can be modified and improved by ordinary knowledge in the art within the technical idea of the present invention. .

[0016]

As described in detail above, according to the present invention, the phenomenon that the critical dimension is changed by the lower film can be improved by detecting the reflected light reflected from the lower film and adjusting the exposure amount based on the detected light. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an exposure apparatus of the present invention including a reflected light detector.

FIG. 2 is a view showing a reflected light distribution map analyzed by a reflected light analyzer of the exposure apparatus of FIG. 1;

FIG. 3 is a view showing a wafer prepared for performing exposure with the exposure apparatus according to the present invention.

FIG. 4 is a view showing the reflectance depending on the thickness of the nitride film of FIG. 3;

FIG. 5 is a view showing critical dimensions depending on the thickness of the nitride film of FIG. 3;

FIG. 6 is a view showing still another wafer prepared for performing exposure by the exposure apparatus according to the present invention.

FIG. 7 is a graph showing the reflectance depending on the thickness of the oxide film and the nitride film in FIG.

FIG. 8 is a diagram showing exposure energy depending on the thickness of the oxide film of FIG. 6 for having an appropriate line width.

FIG. 9 is a flowchart shown to explain an exposure method using the exposure apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 motor 3 wafer 5 light source 7 half mirror 9 mask 11 lens 13 reflected light detector 15 reflected light analyzer 17 exposure controller 19 shutter

Claims (6)

[Claims] 1. A wafer on which a photoresist film is formed
An exposure apparatus comprising: a support base that can be moved in the X-axis and the Y-axis; a mask that selectively transmits light to the wafer; and a light transmission unit that can transmit light to the mask. A reflected light detector that can detect the reflected light reflected by the lower film, a reflected light analyzer that can analyze the reflected light from the reflected light detector to obtain a reflected light distribution map, and an analyzer that uses the reflected light analyzer An exposure controller for adjusting an exposure amount based on the reflected light distribution map. 2. The exposure apparatus according to claim 1, wherein the lower film is a nitride film or a composite film of an oxide film and a nitride film. 3. The exposure apparatus according to claim 1, wherein the support table can be moved in X and Y axes using a motor. 4. A step of providing a desired mask in an exposure apparatus including a reflected light detector; a step of loading a test wafer having a photoresist in a wafer lot on a support table of the exposure apparatus; Detecting the reflected light reflected by the lower film formed under the photoresist at the time of exposure by sectioning and exposing the wafer to the X axis and the Y axis, and detecting the reflected light by the reflected light detector. Analyzing the reflected light with a reflected light analyzer to obtain a reflected light distribution map of the test wafer; unloading the test wafer; and loading a first wafer in a wafer lot on the support. Subjecting the first wafer to X-axis and Y-axis divisional exposure while adjusting the amount of exposure according to the reflected light distribution map analyzed on the test wafer; Unloading a first wafer; and performing the same exposure as the first wafer from the second wafer to the last wafer in the wafer lot. Method. 5. The exposure method according to claim 4, wherein the lower film is a nitride film or a composite film of an oxide film and a nitride film. 6. The exposure method according to claim 4, wherein the adjustment of the exposure amount is performed using an exposure controller and a shutter connected to the reflected light analyzer.