JP2587943B2 - Method for cleaning back surface of semiconductor wafer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a photosensitive photoresist used for forming a circuit pattern on a semiconductor wafer or a semiconductor substrate (hereinafter simply referred to as a wafer) in a process of manufacturing a high-density integrated circuit. The fine powder that has peeled off (hereinafter simply referred to as resist) first adheres to the back surface of the wafer, and in the subsequent process, the fine powder of the resist adheres to the circuit pattern on the wafer surface and masks it, thereby causing defects in the circuit pattern. The present invention relates to a method of cleaning the rear surface of a wafer to prevent the occurrence of the product from lowering the yield.

(Prior art) Conventionally, in order to form a circuit pattern on a wafer, a resist film is applied to the surface of the wafer, prebaked (preheated), and then exposed to ultraviolet light through a glass or reticle original plate depicting the circuit pattern. And developed (including rinsing, the same applies hereinafter) {see N in FIG. 3 (a)).

In recent years, integrated circuits have tended to become ultra-high-density, and circuit patterns have become ultra-miniaturized with this trend, but positive resists are generally used as resists for forming the circuit patterns. A quinone diad-based resin is mainly used for the positive resist. This kind of resin has the property that the resin itself is hard and brittle. Therefore, if any mechanical shock is applied in the circuit pattern forming process, the applied resist is easily peeled finely and turned into dust (hereinafter, referred to as “ This is called a resist dust), which operates as a mask, and lowers the yield in forming a circuit pattern. Hereinafter, this will be described in detail.

FIG. 4 is an apparatus sectional view showing a conventional photolithography process.

First, in FIG. 4 (a), 1 is a wafer,
A pattern of the exposed resist 2 is formed on the front surface, and a large number of resist dusts 3 generated during the process adhere to the back surface. In the resist developing step, the wafer 1 is adsorbed on the rotating body 5 fixed on the rotating shaft 4 by the vacuum suction pipe 7 in the direction of the vacuum suction indicated by the arrow 6 and rotated. 9 is squirted.

In order to clean the developing solution 9 that has flowed to the back surface, a rinse 10 is performed on the back surface of the wafer. However, the resist dust 3 adhering to the back surface cannot be removed. Adhere to the part as it is. The remaining resist dust 3 is then sucked by the suction portion and transferred and adheres to another wafer to be developed.

FIG. 4B is a sectional view of the apparatus showing a wafer baking step after development. The developed wafer 1 is attracted to the hot plate 11, but also at this time, the resist dust 3 adhered to the back surface of the wafer 1 is transferred and adhered to the surface of the hot plate 11, and further, the next attracted wafer Adheres to Reference numeral 12 denotes a resist pattern after development.

FIG. 4 (c) is a cross-sectional view in which a plurality of wafers 1 on which development has been completed are housed in a wafer cassette 13. Also at this time, the resist dust 3 attached to the back surface of the wafer due to the mechanical vibration during transportation is changed to the lower wafer 1.
Drops and adheres to the surface of.

As described above, in the processes such as etching and ion implantation in the conventional semiconductor circuit pattern forming process, the resist dust 3 adheres to the wafer 1 and remains on the circuit pattern to serve as a mask, thereby increasing the product yield. Is causing a decrease.

(Problems to be Solved by the Invention) As described above, the resist dust 3 adhering to the wafer 1 is required to be further miniaturized in the future, and is an extremely large problem in the field of semiconductor integrated circuit manufacturing which is progressing. Particularly, the residue of the resist dust attached to the back surface of the wafer, which cannot be easily cleaned by rinsing or the like, is a very serious problem for forming a circuit pattern to be miniaturized.

 An object of the present invention is to eliminate the above problems.

(Means for Solving the Problems) The present invention aims at the above object by focusing on the fact that the resist dust 3 adhering to the back surface is the same material as the resist on the front surface, as shown in the cross section in FIG. Then, the exposure 15 of the backside resist is performed on the resist dust 3 in the same manner as the exposure of the frontside resist 14 (FIG. 1A), and then the wafer is developed and rinsed to remove the resist dust 3. 1 (FIG. 1 (b)).

(Operation) According to the present invention, since the resist dust 3 does not adhere to the back surface of the wafer 1, the wafer suction stage 16 or the hot plate 11
The transfer of the resist dust 3 to the surface of the wafer and other surfaces of the apparatus in contact with the wafer surface does not occur.
Even if a plurality of wafers 1 are accommodated in the wafer cassette 13 in multiple stages, the resist dust 3 does not fall from the back surface of the upper wafer 1 to the surface of the lower wafer 1 and does not adhere thereto.

Therefore, always clean equipment or wafer cassette
13 enables the formation and movement of circuit patterns.

That is, the present invention reduces the residue of the resist dust 3 adhering to the wafer surface so as to be extremely small, eliminates an adverse effect on an etching step, an ion implantation step, and the like of integrated circuit manufacturing, and therefore can improve the product yield. .

(Example) Hereinafter, the present invention will be described with reference to the drawings using examples.

FIG. 2 is a process drawing showing one embodiment of the present invention, and reference numerals which are not described below have the same or the same functions as in the preceding figures.

First, in FIG. 2 (a), reference numeral 17 denotes a support claw for supporting only a part of the edge of the wafer 1, and the back surface of the wafer 1 is exposed in this state. The exposure wavelength is a g-line (λ = 436 nm) having the same ultraviolet light wavelength as the exposure of the surface resist 2, or a strong ultraviolet light.

Further, similarly, the position of the support claw 17 is changed, and the unexposed portion thereunder is also exposed.

Next, as shown in FIG. 2B, the back surface of the wafer 1 is developed. Reference numeral 18 denotes a suction table for the wafer 1, which sucks the wafer 1 from the vacuum suction hole 19 and ejects the developing solution or rinsing liquid from the rotating spray nozzle 21 which is inserted into the waste liquid pipe 20 and rotates. The exposed resist dust 3 on the back surface of the wafer is developed and decomposed, and a waste liquid pipe 20 is formed.
Wash off from.

FIG. 2 (c) shows the cleaning of the edge portion of the wafer in contact with the suction table 18, and at the same time as the normal development of the front surface, only the peripheral portion of the rear surface is developed by the nozzle 22 dedicated to the rear surface. The resist dust 3 that has been transferred from the other wafer 1 that has been previously absorbed is cleaned.

FIG. 2 (d) shows the wafer 1 cleaned by the exposure and development of the back surface as described above.
According to the present invention, no resist dust 3 exists on the back surface of the wafer.

FIG. 3 is a flow chart showing the sequence in which the present invention is carried out in the step of forming a semiconductor circuit pattern. The backside exposure and the development of the present invention are carried out before the photolithography step shown in FIGS. Alternatively, it can be performed between exposure and development of the wafer surface {FIG. (B)}, performed after development of the surface (FIG. (C)), or any other process sequence that matches the process. Also, the backside exposure I
If performed prior to II, each can be separated and performed over other photolithographic steps (III-VI),
It is possible to remove resist dust attached to the wafer surface.

(Effects of the Invention) As is apparent from the above description, the present invention exposes and develops the back surface of the wafer to decompose and wash away the resist dust attached thereto, thereby minimizing the resist dust attached to the back surface of the wafer. That, the wafer with very little resist dust, in the subsequent process, without transferring the resist dust to other wafers in the wafer suction stage, or even if multiple wafers are accommodated in the wafer cassette, Since there is no resist dust falling, the wafer can be moved while being kept clean. As a result, the occurrence of defective products due to the intrusion of the resist dust in the etching or ion implantation stage is extremely reduced, and the effect of the implementation is great.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the method of the present invention, FIG. 2 is a sectional view specifically showing the present invention, FIG. 3 is a flow chart of the method of the present invention, and FIG. It is sectional drawing explaining. 1 ... (semiconductor) wafer, 2 ... resist, 3 ... resist dust, 4 ... rotating shaft, 5 ... rotating body, 6 ...
Vacuum suction direction, 7: Vacuum suction pipe, 9: Developer (including rinsing liquid), 11: Hot plate, 12 ...
Resist pattern, 13 wafer cassette, 17 support claws, 18 suction table, 19 vacuum suction hole, 20 waste liquid pipe, 21 spray nozzle for back surface, 22 nozzle for exclusive use of back surface periphery.

Claims (1)

(57) [Claims] 1. A cleaning method for removing resist dust attached to a back surface of a semiconductor wafer in a step of forming a circuit pattern on a surface of a semiconductor wafer or a semiconductor substrate using a positive photoresist, Exposing the back surface of the semiconductor wafer by supporting a part of the back edge of the semiconductor wafer with a support claw; and exposing the support claw by changing the position of the support claw supporting the back edge of the semiconductor wafer. Exposing the back surface portion of the semiconductor wafer that has not been subjected to the process, and decomposing and removing the resist dust by developing the entire back surface of the semiconductor wafer. .