JP3348842B2 - Method of forming spin coating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a spin coating film on a wafer, and more particularly to a method for forming a spin coating film useful as a method for forming an antireflection film formed under a photoresist for ultraviolet exposure. It relates to a forming method.

[0002]

2. Description of the Related Art Higher performance and higher integration of semiconductor integrated circuit devices are continually being promoted, and contact hole diameters and processed line widths are steadily miniaturized. In lithography technology for processing such fine dimensions with high precision, the wavelength of exposure light has been shortened, and deep ultraviolet light exposure using a KrF excimer laser having a wavelength of 248 nm or an ArF excimer laser having a wavelength of 193 nm has become common. ing. Thus, in the excimer laser light, the reflectivity on the substrate is larger than that of the conventional i-line, and the standing wave effect caused by the interference between the incident light and the reflected light from the interface between the resist and the substrate appears remarkably. Therefore, the use of an antireflection film is essential. The anti-reflection film is classified into an organic type and an inorganic type depending on the material, and is divided into a top type and a bottom type according to a difference in a formation position with respect to a photoresist. Among them, a bottom type formed by spin coating under a photoresist film is used. Organic bottom anti-reflection coating (hereinafter referred to as BARC) is most widely used.

FIG. 3 is a flowchart showing a method of forming a resist pattern using BARC. An organic lower layer anti-reflective coating solution (hereinafter referred to as a BARC solution) is dropped on a wafer on which a film to be processed such as an insulating film or a conductive layer is formed, and the BARC having a substantially flat upper surface is formed by rotating the wafer. . After baking the applied BARC, a photoresist is spin-coated thereon. After pre-baking the photoresist, exposure is performed and post-exposure baking is performed. Subsequently, development is performed to obtain a photoresist film having a desired pattern.
Then, using this resist film as a mask, BARC is etched to process the BARC into the same pattern as the resist film. Thereafter, the film to be processed on the wafer is processed.

FIG. 4 is a sectional view of a conventional BARC formation method in the order of steps. As shown in FIG. 4A, a wafer 2 that needs to be subjected to photolithography is mounted on a turntable 1, and a BARC liquid is dropped from a BARC liquid nozzle 3 to a substantially central position on the wafer 2. Next, FIG.
As shown in FIG.
(Using 0 rpm) to spread the BARC solution evenly on the wafer 2. Then, the main rotation (rotation speed 1500 to 500
0 rpm), and as shown in FIG.
BARC4 having a desired film thickness is formed. At this time BARC
Since the liquid also circulates on the backside of the wafer, B
ARC4 is formed.

The BARC adhered to the wafer edge portion and the wafer back surface is a film unnecessary for lithography, and the film adhered to the BARC is removed in a wafer transfer step, a cleaning step, and the like, thereby causing generation of particles. There is a need. Therefore, as shown in FIG. 4D, while rotating the wafer (using a rotation speed of 1000 to 2000 rpm), the organic solvent is dropped on the wafer edge portion by the organic solvent nozzle 5 and the organic solvent nozzle 6 is applied to the back surface of the wafer. Also sprays an organic solvent to remove the BARC on the wafer edge and wafer back. Table 1 is a table showing an example of a spin coating sequence used in a conventional technique when forming a BARC. A method for forming such a BARC is known, for example, from Japanese Patent Application Laid-Open No. H11-218933.

[0006]

[Table 1]

[0007]

The above-mentioned prior art has the following problems. FIG. 5 is a cross-sectional view in the order of steps for explaining this problem. In the prior art, in order to remove unnecessary BARC4 at the wafer edge, FIG.
As shown in (a), an organic solvent is dropped on the wafer edge portion by an organic solvent nozzle 5 to remove unnecessary BARC. At this time, the BARC4 in the portion where the organic solvent was dropped
Is melted, part of the BARC 4 contracts due to surface tension, and a bulge 4a is generated at the end of the BARC. The BARC after the main rotation has a low fluidity due to evaporation of the solvent, and the number of rotations at the time of removing the BARC at the wafer edge is not as high as the main rotation.
Remains as it is. The bulge 4a reaches ten times the film thickness at the central portion of the wafer, and remains without being completely removed by etching after the development of the photoresist. As a result, the film to be processed (conductive film or insulating film) under the ridge 4a remains without being removed even in the etching process of the film to be processed performed after the photolithography process. The remaining film to be processed accumulates and becomes thicker as the photolithography process is repeated, and peels off in the transporting process and the resist film peeling / cleaning process, and becomes a source of contamination on the production line. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to remove a bulge formed at an end of a BARC when an unnecessary part of the BARC is removed. Another object of the present invention is to prevent the generation of particles that become a source of contamination in a production line.

[0008]

According to the present invention, in order to achieve the above object, (1) a step of dropping a material for forming a spin coating film on a wafer; and (2) rotating the wafer. Stretching the dropped spin coating film forming material to form a spin coating film; and (3) removing the spin coating film at the wafer edge by dropping a solvent onto the wafer edge while rotating the wafer. (4) a step of shaking off the solvent remaining on the wafer due to the rotation of the wafer; and (5) a rotation number higher than the rotation number in the step (4).
Rotate the wafer to form on the spin coating film in the previous process
(6) a step of dropping a solvent again on the wafer edge portion while rotating the wafer to remove the spin coating film on the wafer edge portion. A method for forming a film is provided.

[Operation] B by the spin coating of the present invention described above.
According to the ARC forming method, the BARC at the wafer edge is leveled at a higher rotation speed than the stretching rotation, and then the BARC flowing to the wafer edge is removed again.
At this time, since the film thickness of the BARC flowing to the edge of the wafer is reduced due to the leveling rotation of the swelling and the organic solvent is shaken off smoothly from the first time, the BARC is removed after the second time BARC removing step. Protrusion hardly occurs at the end of the BARC, and film peeling is eliminated.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in the order of steps showing an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the wafer edge portion in an enlarged order, in the order of steps of the embodiment of the present invention. First, a wafer 2 to be subjected to photolithography processing is mounted on a turntable 1 and a BARC liquid nozzle 3 is mounted.
The BARC solution is dropped almost at the center of the wafer 2 [FIG.
(A)].

Subsequently, the BARC liquid is stretched and rotated (using a rotation speed of 1000 to 2000 rpm) to perform BAR.
The liquid C is spread on the wafer to a uniform film thickness. Next, an organic solvent is dropped on the wafer edge from the organic solvent nozzle 5 to remove the BARC at the wafer edge [FIGS. 1 (b) and 2].
(A)]. The horizontal distance of the organic solvent nozzle 5 from the wafer edge at this time is defined as L1. After the completion of the dropping of the organic solvent, the wafer is rotated for 2 to 4 seconds (rotation speed 1000 to 2).
000 rpm) and shake off the organic solvent. The thickness of the BARC4 to be formed is almost determined by the number of rotations in this step.

As shown in FIG. 2B, also in the present invention, at the time of the first removal of the BARC at the wafer edge, the BARC in the portion where the organic solvent has been dropped is melted and the BARC is partially removed due to surface tension. The part shrinks in the direction of the arrow and rises. At this point, the solvent has not been completely evaporated, and fluidity still remains in the bulge 4a of the BARC. Therefore, before the solvent is completely evaporated, the rotation speed (rotation speed 2000 to 4000 r) is higher than that at the time of shaking off the organic solvent.
pm) and rotate the wafer to B at the wafer edge.
Equalize ARC excitement. At this time, as shown in FIG. 2C, the bulge of the BARC at the wafer edge portion flows outward and becomes thinner and reaches near the wafer edge.

Next, as shown in FIGS. 1 (d) and 2 (d), the organic solvent is dropped from the organic solvent nozzle 5 to remove the BARC flowing out to the wafer edge (FIG. 2 (e)).
(Use the number of revolutions 1000-2000 rpm). At this time, as shown in FIG. 1 (d), the solvent which is sprayed from the organic solvent nozzle 6 from the back surface of the wafer and the BARC which has wrapped around the back surface of the wafer is also removed. Assuming that the horizontal distance of the organic solvent nozzle 5 from the wafer edge in this step is L2, L1> L2. That is, the second organic solvent dropping position is outside the wafer from the first time. Also,
Since the thickness of the BARC to be removed for the second time is smaller than that for the first time, the amount of the organic solvent dropped for the second time is smaller than that for the first time. After dropping and jetting of the organic solvent are completed, the solvent is shaken off for a predetermined time (rotation speed: 1000 to 20).
00 rpm). In the present invention, the BARC film thickness is determined by the number of rotations from the elongation rotation after dropping of the BARC solution to the shake-off of the solvent. Therefore, it is necessary to control the viscosity of the BARC liquid so that a desired film thickness is obtained at these rotation speeds. In addition, in order for the BARC to have fluidity, the time from the elongation rotation to the solvent shake-off rotation must be within 15 seconds in order to enter the leveling of the wafer edge.

[Embodiment] Table 2 is a table showing a spin coating sequence according to an embodiment of the present invention. In this example, when an 8 inch (20.3 cm) wafer was used to form a coating film according to the sequence shown in Table 2, a BARC having a thickness of 0.1 μm and a uniform film thickness without any swelling was obtained.

[0015]

[Table 2]

Although the preferred embodiments and examples have been described above, the present invention is not limited to these examples, and can be appropriately modified without departing from the gist of the present invention. It is. For example, in the embodiments, the method of forming the BARC has been described. However, the present invention is not limited to this, and can be applied to all methods of forming a coating film formed by a spin coating method such as a photoresist coating method. . Further, in the embodiment, the removal of the BARC on the back surface of the wafer is performed at the same time as the second dropping of the organic solvent. You may make it perform simultaneously with the solvent dripping of the 2nd time. In addition, when the BARC does not reach the wafer edge due to the swelling rotation, the second solution dropping step can be omitted. Further, the solvent swing-off rotation after the first organic solvent dropping step may be omitted as appropriate, and the BARC at the wafer edge may be extended by performing high-speed rotation immediately after the completion of the solvent dropping.

[0017]

As described above, in the method for forming a spin coating film according to the present invention, the spin coating film forming material is dropped, the spin coating film is stretched, the spin coating film is removed from the wafer edge portion with a solvent, and the spin coating film is stretched. The BARC at the wafer edge is smoothed at a higher rotation speed than the rotation speed, and the coating film flowing to the wafer edge portion is removed again if necessary. A film can be formed. Therefore, according to the present invention, it is possible to prevent the film to be processed remaining on the wafer edge portion without being etched and increasing the film thickness, thereby preventing the production line from being contaminated by film peeling.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (part 1) showing the embodiment of the present invention in the order of steps.

FIG. 2 is a sectional view (part 2) showing the embodiment of the present invention in the order of steps.

FIG. 3 is a flowchart showing a photolithography process using BARC.

FIG. 4 is a sectional view showing a conventional example in the order of steps.

FIG. 5 is a cross-sectional view for explaining a problem of the conventional example.

[Explanation of symbols]

Reference Signs List 1 turntable 2 wafer 3 BARC liquid nozzle 4 BARC (organic lower anti-reflection film) 4a BARC swell 5, 6 organic solvent nozzle L1 Distance from wafer edge to organic solvent nozzle 5 when first dropping organic solvent L2 2 The distance from the wafer edge to the organic solvent nozzle 5 when the organic solvent is dropped for the second time (L1> L2)

Claims (9)

(57) [Claims] (1) a step of dropping a spin-coating film forming material on a wafer; and (2) a step of stretching the spin-coating film-forming material dropped by rotating the wafer to form a spin-coating film. (3) a step of dropping a solvent on a wafer edge while rotating the wafer to remove the spin-coated film on the wafer edge; and (4) a step of shaking off the solvent remaining on the wafer due to rotation of the wafer. ( 5) At a rotation speed higher than the rotation speed in the step (4).
Rotate the wafer to form on the spin coating film in the previous process
(6) a step of dropping a solvent again on the wafer edge portion while rotating the wafer to remove the spin coating film on the wafer edge portion. Method of forming a film. 2. At least in the step (3) or the step (6), a solvent is poured also into an edge portion of the back surface of the wafer to simultaneously remove the spin coating film formed on the back surface of the wafer. The method for forming a spin coating film according to claim 1, wherein: 3. The method according to claim 1, wherein the dropping position of the solvent in the step (3) is closer to the center of the wafer than the dropping position of the solvent in the step (6).
Or the method for forming a spin coating film according to 2 above. 4. The rotation according to claim 1, wherein the amount of the solvent dropped in the step (3) is larger than the amount of the solvent dropped in the step (6). A method for forming a coating film. 5. The method according to claim 1, further comprising adding a solvent shake-off step following the second solvent dropping step, wherein the number of rotations in the second solvent shake-off step is lower than the number of rotations in the first solvent shake-off step. The method for forming a spin coating film according to claim 1. 6. The number and time of rotation of the wafer in each of the steps (2) to (4), and the viscosity of the spin coating film forming material, The method for forming a spin-coated film according to any one of claims 1 to 5, wherein the thickness of the spin-coated film is set to a desired film thickness after completion. 7. The method according to claim 6, wherein the number of rotations in the step (2) and the step (3) or the number of rotations in the step (2) to the step (4) is equal. The method for forming a spin coating film according to claim 1. 8. The spin coating according to claim 1, wherein a total time from the step (2) to the step (4) is within 15 seconds. Method of forming a film. 9. The method for forming a spin coating film according to claim 1, wherein said spin coating film is an organic anti-reflection film formed under a photoresist film.