JP2770338B2 - Development method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a developing method. In particular, the present invention relates to a developing method having good uniformity of development.

[Summary of the Invention]

The present invention performs a pre-wet process by supplying pure water to the surface to be processed of the object to be processed, and further supplying pure water and a developing solution to the surface to be processed, and then drying the surface to be processed. After that, the surface to be processed is developed with a developer so as to improve the uniformity of development and the like.

[Conventional technology]

In the development technique, it is desired that uniform development be performed. Further, when a pattern having a specific shape is obtained by development, it is desired that the controllability of the shape is good and the shape does not deteriorate.

For example, the prior art will be described as follows using a developing method used in a lithography step in a semiconductor manufacturing process as an example of a developing method of pure water. Generally, in this type of lithography process, a resist (photosensitive resin) is applied to a surface to be processed, baked or the like if necessary, and then exposed using a mask having a desired pattern, and developed after the exposure. To obtain the desired shape.

As a technique in this field, for example, there is paddle development as a method of developing a positive resist after exposure.

Paddle development is to use the surface tension of the developing solution to pour the developing solution on the surface of the wafer to be processed,
It is a method of developing while stationary (for example, Japanese Patent Publication No. 60-5330).
No. 5).

FIG. 4 shows a basic method of the conventional paddle development.
In this method, first, as shown in FIG.
While rotating the wafer a, the developer b is dropped onto the wafer a from the liquid spray c. Reference numeral d denotes a table (wafer chuck) for supporting the wafer a, which is rotated as shown by an arrow e to rotate the wafer a. By rotating, the developer b is spread over the entire surface of the wafer a, and as shown in FIG. 4 (b), the developer b is mounted on the surface to be processed of the wafer a by utilizing its surface tension, that is, so-called liquid filling is performed. And, in this state, it is left still.

However, simply rotating the wafer a and dropping the developing solution deteriorates the uniformity of the developed resist within the wafer surface, particularly the line width uniformity when the resist remains in a linear shape. Therefore, pre-wet (Pre we
t) is used.

This method will be described below with reference to FIG.

The pre-wet method is as follows. First, as shown in FIG. 5 (a), a table (wafer chuck) d holding a wafer a is rotated by an arrow e to rotate the wafer a, and the pure water nozzle f Dispense pure water g. Thereafter, as shown in FIG. 5 (b), the pure water g and the developing solution b from the developing solution spray c are simultaneously discharged. As the developer spray c, a high pressure spray is usually used, and the developer is sprayed over the entire surface of the wafer in a dew state. Thereafter, as shown in FIG. 5 (c), only the developer b is discharged and the developer is poured on the wafer a.

In this method, as described above, the liquid on the wafer a is initially pure water g. Thereafter, as the time elapses, the developing solution gradually becomes thicker, and finally becomes the developing solution b discharged from the spray c.

By doing so, the spread of the developing solution b can be improved, and the adaptation of the developing solution b can be improved, and the development proceeds almost simultaneously over the entire area of the wafer a. Therefore, development with good uniformity can be achieved. The line width becomes uniform.

[Problems to be solved by the invention]

However, when the paddle development using the pre-wet method is performed, although the line width uniformity is improved, there is a problem that the resist shape is deteriorated.

This problem will be described below with reference to FIGS. 6 and 7.

When developing resist in the photolithography process,
For example, when development is performed using a positive resist, the shape of the positive resist after development generally has a trapezoidal shape with a narrow upper width b and a wider lower width a, as shown in FIG. As one of the causes, the light for exposure applied to the resist is
It is considered that the sharpness may be lost due to diffraction, as shown in FIG. 7 (b). That is,
Immediately below the reticle, as shown in FIG. 7 (a), the light intensity shows a rectangular intensity distribution with a sharp boundary between where the light hits and where it does not hit. However, the light radiated from the reticle onto the wafer through an optical system such as a lens usually loses sharpness due to diffraction or the like on the way, and has a curved intensity distribution as shown in FIG. 7 (b). Become. As a result, the resist exposed by light irradiation having the light intensity distribution shown in FIG. 7B is considered to inevitably become trapezoidal (see FIG. 6), reflecting the light intensity distribution.

In the case of the conventional pre-wet method described above, although the cause is not necessarily clear, it is considered that the above-described resist shape deterioration occurs in an amplified form.

The present invention solves the above-mentioned problems, and has good uniformity of development. Therefore, when uniformity of line width is required, the uniformity is good. ) It is an object of the present invention to provide an excellent developing method without shape deterioration.

[Means for solving the problem]

The developing method of the present invention is a method of developing a processed object, comprising: supplying pure water onto a processed surface of a processed object, and further supplying pure water and a developing solution to the processed surface. Perform a pre-wet process in, after drying the surface to be treated,
The surface to be processed is developed with a developing solution, thereby solving the above-mentioned problem.

That is, as shown in FIG. 1, in the developing method of the present invention, after a pre-wet treatment step I (denoted as a low-concentration developer treatment) using pure water and a developer, a drying step II is performed once, and then the developer In the developing step III (denoted as development with a high-concentration developer).

In the present invention, for example, after pre-wetting with pure water and a developing solution, the drying may be performed once, and then the developing solution may be added to the liquid and processed with a high-concentration developing solution.

Further, after the pre-wetting, the developing solution at the time of the pre-wetting may be quickly removed by flowing water, and then dried, and the developing solution may be loaded.

Further, the processing step I and the drying step II may be repeated, and for example, pre-wet-dry may be repeated several times.

The present invention can be applied to paddle development in which a developer is filled as described above, and can be used to prevent shape deterioration.However, as exemplified in Examples described later, the present invention is not limited to paddle development. Absent.

[Function] In the developing method of the present invention, the processing with the low-concentration developer is performed prior to the development with the high-concentration developer, so that the developer is uniformly spread over the surface to be developed, so that the familiarity is good and, therefore, the uniformity is improved. High development can be achieved. This can be satisfied even when uniformity of line width is required.

Further, after the low-concentration developer treatment, drying is performed prior to the development with the high-concentration developer, whereby a good shape after development without shape deterioration can be obtained. The conventional problem of shape deterioration when a resist, particularly a positive resist, is used is solved.

The effect of improving the shape by including the drying step is not necessarily clear, but is considered to be due to the following. That is, taking a positive resist as an example, the development is based on the "dissolution suppression reaction" due to the coupling of the unreacted photosensitive agent and the polymer, and the "dissolution promoting effect" due to the lowering of the interfacial tension due to the elution of the photoreacted photosensitive agent. And is considered a conflict.

Immediately after the start of development, a dissolution inhibition reaction occurs first, and then
As the dissolution proceeds, the dissolution promoting effect also increases.

Now, once the developing solution is shaken off by drying once during development, the eluted photosensitizer is also removed, and when developing with a high-concentration developer (for example, when the solution is filled), the dissolution inhibition reaction is considered to be the main reaction. Can be

Therefore, the dissolution rate of the upper portion of the resist decreases. It is presumed that this improves the shape.

The present invention has been made based on the following findings by the present inventors. That is, even when using a light intensity distribution that has lost sharpness as shown in FIG. 7 (b), if the resist is to be formed into a sharp rectangle, the dissolution rate at the top of the resist is reduced, and the dissolution rate at the bottom of the resist is reduced. Must be raised.

On the other hand, the development speed of a resist, particularly a positive resist, decreases when the development is stopped in the middle. For example, comparing the case of a development time of 40 seconds with the case of repeating the development time of 20 seconds twice,
The line width is clearly wider twice per second. This means that once the development has been stopped, this slows down the dissolution rate, presuming that the above-mentioned action is correct.

Therefore, after processing with a low-concentration developing solution, once drying is performed, and then development with a high-concentration developing solution such as a puddle is performed, the drying slightly dissolves the region in the low-concentration developing solution processing, that is, dissolves the upper portion of the resist. Speed will drop. Therefore, the distribution of the dissolution rate is corrected so as to be smaller at the upper part of the resist and larger at the lower part of the resist.

It is considered that the shape is corrected by such an operation, and a sharp rectangular resist is obtained.

Moreover, in the present invention, processing with a low-concentration developer is performed as pre-wet processing by first supplying pure water to the surface of the object to be processed, and then applying pure water and the developer to the surface to be processed. Supplying, drying, and then supplying only the developer to the surface to be processed is performed, so that the advantage of the pre-wet method is brought about, and the effect of realizing uniform development over the entire surface to be processed can be realized. It becomes even more noticeable. Further, in this case, a good sharp rectangular resist shape can be obtained as described above, so that the difficulty of the conventional pre-wet method in which the resist shape is deteriorated can be solved.

〔Example〕

Hereinafter, embodiments of the present invention will be described. Note that, needless to say, the present invention is not limited to the embodiments described below.

Example 1 FIG. 2 shows the present invention applied to the development of a resist in a photolithography step in a semiconductor manufacturing process. In particular, it is embodied in paddle development.

In the present embodiment, pure water 4 is first supplied from a pure water nozzle 2a onto a processing surface 1a of a wafer which is a processing target 1 (FIG. 2 (a)). Are supported by a wafer chuck, which is a table 3 on which this is mounted. By rotating the table 3 as indicated by an arrow 5, the object 1 is rotated.

After the pure water 4 is supplied to the surface to be processed, the developer 6 is supplied to the surface 1a from another developing nozzle spray 2b while continuing to supply the pure water 4. The developer 6 may be supplied in a small amount. For example, the developer diluted with the pure water 4 may have an extremely low concentration. The developer is at high pressure
The mist is sprayed over the entire surface to be processed 1a. Therefore, a high pressure spray was used as the developer spray 2b.

Thereafter, as shown in FIG. 2C, the supply of the pure water 4 is stopped, and the supply of only the developer 6 is performed.

In the process using the low-concentration developer, it is not always necessary to separately supply the developer and pure water, but by performing the above, the pre-wetting effect can be enhanced.

Next, drying is performed once (FIG. 2 (d)). Drying can be achieved by, for example, rotating the table 3 to shake off the liquid from the processing target 1. FIG. 3 (d) schematically shows such a method. Also, such rotation and the supply of hot air can be used in combination. In addition, a heater or the like may be used. In order to accelerate the drying, such forced drying means or such means may be used in combination with rotation.

Next, as shown in FIG. 2E, the developing solution 7 is applied to the surface 1a to be processed.
To supply. Here, the developing solution 7 was applied from a developing solution nozzle 2c different from the spray 2b. The developer 7 may be thicker than the developer diluted with the pure water. Therefore, the concentration may be the same as that of the developer 6 given together with the pure water. Therefore, the spray 2b may be used without using another nozzle 2c. However, in FIG. 2 (e), since the developer 7 is filled, another nozzle 2c is used to facilitate this. During this time, the object to be developed 1 is kept rotating.

Next, as shown in FIG.
Allow development to proceed.

Thereby, uniform development can be achieved, and a resist having good uniformity in line width can be obtained. Moreover, there is no deterioration in the shape of the resist, and a sharp rectangular shape can be obtained.

That is, in the present embodiment, after performing the pre-wet of FIGS. 2A to 2C for 3 seconds, the second rotation is performed at a high speed for 10 seconds.
As shown in FIG. 6 (e) and FIG. 6 (f), the liquid was dried as shown in FIG.
The ratio was improved from 0.8 (conventional) to b / a = 0.94 (this embodiment).

Such an improvement is extremely effective in a technique for forming a fine pattern.

As shown in FIG. 5, in the conventional example used for the above comparison, after the pre-wet (FIG. 5 (b)), the developing solution is filled and developed without taking a drying step (see FIG. 5). FIG. 5 (c)).

In the present embodiment, a positive resist was used as a photosensitive agent to be developed on the surface to be processed 1a. Any resist can be used as the positive resist. For example, typically, a photosensitive resin having a novolak resin as a base material and naphthoquinone azide as a photosensitive agent can be used. In addition, a polymethyl methacrylate-based or polymethylpropenyl ketone-based positive resist can be used.

This may be performed using a negative resist. Examples of the negative resist include polyglycidyl methacrylate, cyclized polyisoprene, polychloromethylstyrene, phenol resin, and chlorinated polystyrene.

The exposure conditions and the type of developer can be appropriately determined depending on the resist used.

Embodiment 2 FIG. 3 shows another embodiment of the present invention. A major difference from the embodiment shown in FIG. 1 is that no liquid reservoir is used.

In the example of FIG. 3, the object 1 to be developed such as a semiconductor wafer supported on a table 3 such as a wafer chuck is placed on a pair of frames 8a and 8b constituting a processing bath as shown in FIG. 3 (b). The processing is performed with the support. That is, as shown in FIG. 3 (b), one of the frames 8a and 8b is used for the object 1 to be developed supported on the table 3 as shown in FIG. 3 (a). The object to be developed 1 is placed, and the other frame 8b surrounds the object to form a bath. In this state, for example, the liquid path provided in the frame 8b
The developing solution 9 can be flowed from 91 to give it on the surface to be processed 1a.

Also in this example, the same effect as in the case where the liquid is filled can be obtained. Example 1 except that the liquid was not poured
Can be performed in the same manner as in Example 1, by supplying pure water and supplying the developing solution in the same manner as in Example 1, performing processing with a low-concentration developing solution,
Thereafter, a configuration in which a high-concentration developer is supplied can be adopted.

In this example, a low-concentration developer is first discharged from the liquid path 91, and then dried, and a high-concentration developer may be discharged from the liquid path 91, or a plurality of liquid paths may be provided. The configuration may be the same as in FIG.

3 (b) is partially omitted from illustration (illustration of the frame on the right side of the figure is omitted), and the frame is illustrated for clarity.
Although the figure is shown as being apart from 8a and 8b, they are in close contact.

〔The invention's effect〕

As described above, the present invention has solved the conventional problems. The uniformity of development is good, and when uniformity of line width is required, the uniformity is good, and the shape of, for example, a resist in the object to be processed is good. An excellent developing method can be provided.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the configuration of the present invention. 2A to 2F show a first embodiment of the present invention in the order of steps. FIGS. 3 (a) and 3 (b) are configuration diagrams showing a second embodiment of the present invention. 4 and 5 show a conventional example. FIG. 6 is an explanatory diagram of a resist shape after development, and FIG. 7 is an explanatory diagram of a light intensity distribution. Reference numeral 1 denotes a processed object (wafer), 1a denotes a processed surface, 2a, 2b,
2c: Nozzle (spray), 3: stand (wafer chuck), 4: pure water, 6, 7: developer, 91: liquid path.

Claims (1)

(57) [Claims] 1. A method for developing an object to be processed, comprising: supplying pure water to a surface to be processed of the object to be processed, and further supplying pure water and a developing solution to the surface to be processed. A developing method comprising performing a wet treatment, thereafter drying the surface to be processed, and then developing the surface to be processed with a developer.