JPH0435018A - Photoresist coating means - Google Patents

Abstract

PURPOSE:To prevent a variation in processing upon alteration of thickness of a resist film and to perform an accurate photolithography technique by sensing information regarding the thickness of a thin film on a wafer, obtaining suitable coating thickness of photoresist to be coated, and coating with the photoresist in the suitable thickness. CONSTITUTION:A board 1 is placed on a stage 6, a film thickness is sensed by a film thickness measuring unit 5 of an objective lens, etc., or an exposure is conducted by a UV exposure unit 4. A conveyed wafer 1 is baked on a hot plate 17 as required, placed on the stage 6, the thickness is measured by the unit 5, it is placed on a spin coater cup 72, spin coated at a suitable rotating speed based on the film thickness to form a photoresist film of the suitable thickness. It is returned to the stage 6, and exposed in suitable exposure amount by the unit 4 so as to correspond to processing in next step. This is to expose to process the film thickness to be measured of the same structure as the part to be actually processed so as to control the thickness of the resist film in next step. Then, the wafer 1 is placed on a hot plate 73, baked, and further conveyed to an exposure unit as required.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to photoresist coating means.

Photoresist is mainly used in photolithography technology to obtain a desired resist pattern by coating it on a substrate to be processed and exposing and developing it.For example, it is used for pattern formation of electronic materials such as semiconductor devices. Although the photoresist application means of the present invention is embodied as a processing means during the process, the photoresist application means of the present invention can be used for general purposes when applying resist in various techniques using photoresists such as those described above.

[Summary of the invention]

The present invention detects information regarding the thickness of a thin film on a substrate to which a photoresist is to be applied, in a resist application means for applying a FNA 1-resist onto a substrate, and based on this, determines the appropriateness of the photoresist to be applied. By determining the coating thickness and applying the photoresist at the appropriate coating thickness, variations in processing dimensions, etc. due to variations in the photoresist coating means are suppressed, and highly accurate patterning is made possible. .

[Conventional technology]

When forming a resist pattern using photoresist, if there is a change in the thickness of the resist film coated on the substrate to be processed, the sensitivity will change, and the shape and dimensions of the resist pattern will change, resulting in a change in the final substrate. This causes variations in machining dimensions.

In other words, since the exposure light used to expose photoresists used in photolithography is generally close to monochrome (single color), standing waves are generated by the reflected light from the substrate, and their interference causes variations in the photoresist film thickness. If there,
Sensitivity fluctuates. In Figure 8, the horizontal axis is the resist film thickness (μm
), and the sensitivity is plotted on the vertical axis in terms of sensing line width (μm), and the relationship is shown below. Figure 8 shows a tungsten silicide WSiX substrate, which is a substrate that reflects almost all light, coated with PFR7750 as a resist. This is the result when exposure was performed. As shown in the figure, as the resist film thickness increases, the sensitivity fluctuates in a wave-like manner with maximum and minimum. The width λ2 between the maxima is approximately 13
00 people, which corresponds to λ1. (n is the refractive index of the resist, in this case 1.64).

Fluctuations in sensitivity result in fluctuations in processed line width. If the resist film thickness varies within a single sample, this will result in processing variations within that sample, impairing the reliability of the sample.Furthermore, if the resist film thickness varies between samples, performance variations will occur between samples. Put it away. As described above, variations in resist film thickness cause variations in sensitivity and processing dimensions, and therefore become very important as variations in processing parameters.

The above sensitivity fluctuation is based on standing wave generation, but this is due to the incident light (
This is due to interference between the exposure light) and the reflected light, and as shown in Figure 8, the light is only λ2/2'1650
Peak-peak is composed of human fluctuations.

From the above, in the lithography process, the sensitivity p
Set the photoresist film thickness aiming at the peak of eak.

However, on the other hand, in an actual semiconductor device structure processed and manufactured using photolithography technology, a transparent thin film (a thin film made of SiO□, SiN, etc.) exists under the resist. That is, if such a thin film does not exist, the result shown in FIG. 4 (
As shown in a), a photoresist 2 (refractive index n, for example, nζ 1.64) is formed directly on the surface of the substrate 1, and as shown in the figure, exposure light is transmitted through the resist 2 and reflected on the surface of the substrate 1. The behavior is as follows. However, in most cases, as shown in FIG. 4(b), a thin film 3 is formed on a substrate 1 (the refractive index n of the thin film 3 is, for example,
□n = 1.45 for film, n for silicon nitride SiN
= 2.00). In this case, since the photoresist 2 is coated on the thin film 3, the behavior is such that reflected light (2) is reflected at the interface with the thin film 3, and reflected light (2) is reflected on the surface of the substrate 1. .

Here, since it is generally reflected light ■ (reflected light ■), the film thickness at which this standing wave interference occurs is not just the thickness of the resist 2;
This is approximately the sum of the thickness of the resist 2 and the thickness of the thin film 3.

Therefore, even if only the thickness of the resist 2 is controlled, if the thickness of the underlying thin film 3 changes, controlling the resist film thickness alone becomes meaningless. In addition, the thickness of the base thin film 3 is ±10% in view of its formation process (oxidation, CVD, etc.).
Fluctuations in degree are unavoidable, and precise control of the thin film 3 cannot be expected.

In the end, in order to solve the above problem, it is sufficient to control the photoresist thickness so that the sum of the film thicknesses of the resist 2 and the underlying thin film 3 is always constant, but as mentioned above, the thickness of the thin film 3 itself Controlling the film thickness is extremely difficult, and no specific means for controlling the film thickness of the resist 2 in this manner has yet been found.

[Purpose of the invention]

The present invention solves the problems of the prior art described above, and even when a thin film is present on the underlying substrate, it is possible to prevent processing fluctuations due to fluctuations in resist film thickness with good controllability, and to achieve even higher precision. The purpose is to provide photolithography technology.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides information regarding the thickness of a thin film on a substrate to which a photoresist is to be applied, in a resist coating means for coating a photoresist on a substrate. Based on this detection, an appropriate coating thickness of the photoresist to be coated is determined, and the photoresist is coated with the appropriate coating thickness.

The configuration of the present invention will be explained as follows using the flow diagram of FIG. 1 showing one embodiment of the present invention, which will be described in detail later.

In the present invention, as illustrated in FIG. 1, information (
In the thin film information detection step I), information regarding the appropriate coating thickness of the photoresist to be coated is determined based on the information H, which is film thickness data, and this information is detected. In the illustrated example, the number of rotations to obtain the film thickness is determined and a control signal (2) is sent to obtain the number of rotations, thereby performing the step (2) of coating the photoresist with the appropriate coating thickness.

[Function] The resist coating means of the present invention detects information regarding the thickness of the thin film on the substrate to which the photoresist is to be applied, determines the appropriate coating thickness of the photoresist to be applied based on this, and determines the appropriate coating thickness of the photoresist to be applied. Since the photoresist is coated at a certain coating thickness, even if a thin film has been formed on the plate in advance, the photoresist film thickness can be controlled at an appropriate film thickness, and therefore variations in resist film thickness can be controlled. As a result, precise machining can be achieved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. However, as a matter of course, the present invention is not limited to the following examples.

Example 1 This example applies the present invention to photolithography technology for semiconductor devices, and more specifically, as a photoresist coating means used when forming a resist pattern on a substrate for forming a semiconductor device. It was used.

In particular, this example measures the thickness of a thin film formed on a semiconductor wafer, which is a substrate, before (or before and after) resist coating, thereby changing the resist coating conditions and achieving a desired resist film thickness with high reproducibility. It is designed to be easily obtained. By effectively utilizing this film thickness measuring means, ll# thickness can be measured even after resist application, and the film thickness after resist application (i.e., the sum of resist thickness and thin film thickness) can be measured, and based on that information, exposure It is also possible to change the intensity (adjust and control the exposure time of the exposure machine) to always obtain a desired constant processing dimension (line width, etc.).

FIG. 1 is a flowchart showing the flow of resist coating using the photoresist coating means of this embodiment.

Further, FIG. 2 illustrates the resist-coated surface of a semiconductor wafer, which is the substrate 1 to be processed.

The photoresist coating means of this embodiment collects information regarding the thickness of the thin film on the substrate 1 (if there is a thin film on the substrate 1, the film thickness or a value serving as a parameter of the film thickness), or information about the thickness of the thin film on the substrate 1, Information giving the appropriate resist film thickness,
Furthermore, when a thin film is not present on the substrate 1, a detection means is provided for detecting information to that effect. In this example,
This detection means is an optical film thickness measuring device. This detection (film thickness measurement) in this embodiment is performed in a pattern-free area around the wafer, as shown by reference numeral 11 in FIG.

This means that the measurement position detection accuracy of the film thickness measuring machine is generally ±5.
Since the diameter is about 0 μm, the measurement substrate is 100 μm.
This is because it requires more than the diameter. The measurement method can be carried out by - an optical interferometry method used in boat fishing (for example, a method used in Dainippon Screen ■'s Lambda Ace, Ten-Two 11's Nanospec, etc.), an ellipsometer, or the like.

The former optical interference method is more common and can be measured more quickly, so it was adopted in this example. A stage equipped with an alignment mechanism according to the outer shape of the wafer is provided in a part of the coater constituting the resist coating means of this embodiment.
The alignment should be approximately ±20 μm in each direction of θ, and the stage movement accuracy should be ±10 μm.
It was designed to have a capability of about μm (see Figure 3).

Note that in FIG. 3, illustration of the stage on which the substrate 1 is placed is omitted). In this embodiment, this stage is provided with a UV exposure machine 4 (details of the configuration will be described later) as schematically shown in FIG. 3, and an objective lens 5 for film thickness measurement, which is a unit for film thickness measurement. Mount. With the above-described design, it is fully possible to mount these UV exposure device 4 and objective lens 5 on the stage.

This makes it possible to measure or expose any part of the wafer, which is the substrate 1, with the U2 light within a positional accuracy of ±50 Ijm.

In this example, since the film thickness information is detected at the periphery of the wafer where there is no pattern, in order to obtain the same information as the actual area to be processed, the detected point is set at the area where the pattern is actually to be formed. The same structure was used to obtain accurate information. That is, regarding the film thickness measuring device which is the thin film film thickness information detection means on the substrate 1 in this example,
In order to more effectively measure the film thickness, in this embodiment, the points at which the film thickness is measured are kept in the same structure as the locations where the pattern to be controlled is formed on the actual device.

In this way, the fifth section describes specific means for making the base film thickness of the part to be measured the same as the part to be actually processed.
This will be explained with reference to Figures (A) and (B).

In FIG. 5(B), a portion to be processed in the central portion Ia (portion to be processed) of the substrate 1 (wafer) is indicated by reference numeral 12. As described above, as a means to keep the film thickness measurement point in the same structure as the location to be controlled, an edge exposure device 4 is provided as shown in FIG. 5(A), thereby performing UV spot exposure. Let's do it. This enables spot exposure to the edge portion 1b (film thickness measurement target portion) of the substrate 1 (wafer), exposes this edge portion 1b, and develops it so that it can have the same structure as the portion to be processed 12. Make it.

As a result, as shown in FIG. 5(B), a structure in which the thin film 32 on the substrate 1 is apertured at the film thickness measurement point 1 is obtained in advance, and the underlying structure is the same as that of the area to be processed 12. Leave it there. Width of film thickness measurement point 11! teeth,
As mentioned above, the thickness is about 100 μm.

FIG. 1 shows the flow of operating procedures when using the photoresist coating means of this embodiment. The present embodiment will be explained as follows with reference to FIG.

First, film thickness information detection I is performed. In this embodiment, as explained using FIGS. 2 and 3, this is a measurement of the thickness of the thin film 3L 32 on the substrate 1 before resist coating. The film thickness data (1) thus obtained is sent to the information processing unit X (in this example, by CPU data processing), and the number of revolutions of the coater for resist application is determined based on this film thickness data (2). This rotational speed is calculated by the information processing section X so that a predetermined resist film thickness can be obtained. This rotational speed control signal (2) is sent from the information processing section X to the rotational speed control section of the coater of the coating means, whereby photoresist coating (2) is performed.

In this embodiment, the substrate 1 coated with the photoresist is further subjected to a film thickness measurement V after coating. Here, data on the sum of the film thicknesses of both the thin film 3L 32 and the coated photoresist film 2 is obtained. The obtained film thickness data (■) is further sent to the information processing section
is sent to a projection exposure device (stepper) serving as an exposure means, and exposure processing (2) is performed for the exposure time.

” Proper exposure is performed from step 2. Development (1) is performed on the substrate (1) to which the appropriate light has been applied. As a result, a substrate 1 on which a desired resist pattern is formed is obtained. Although the baking process is not shown in FIG. 1, the baking process that is used in this type of development may be performed as appropriate.

Furthermore, in this embodiment, the algorithm for determining the rotation speed (its control signal is indicated by ■) during resist application was modified as follows based on the film thickness data (■) after resist application. .

That is, as shown in FIG. 6, the relationship between the number of revolutions and the film thickness of the first resist is determined in advance, and this is input into the information processing section. In FIG. 6, A1-A3 indicate algorithms, A1 is algorithm 1, A2 is algorithm J12, and A3 is algorithm 3. The exposure time control algorithm is based on the line width (which is the vertical axis of the data in Figure 8).
(sensitivity) can be obtained by converting the sensitivity/exposure time. In this case, the completed size data is input to the information processing unit X by some means (the control signal is indicated by reference numeral XI in FIG. 1).

FIG. 7 shows an example of the configuration of a resist coating device that can be used in the above embodiment.

In FIG. 7, 6 is a stage for measurement and UV exposure,
As explained using FIG. 3, the substrate 1 is placed on the stage 6, and the film thickness is detected by the film thickness measurement section 5 such as an objective lens, or exposed by the UV exposure section 4. 7L 734; l Bake phone 1 to play 1, 72 is a spin coater cup. The substrate 1 carried in at 81 is baked on a pot plate 71 if necessary, placed on a stage at 82, has its film thickness measured by the film thickness measuring section 5, and is transferred to a spin coater at 83. The photoresist film is placed on a cup and spin-coded at an appropriate rotational speed based on the film thickness to form a photoresist film with an appropriate thickness. This is returned to the stage 6 at 84, and exposed at the UV exposure section 4 at an appropriate exposure amount in order to be processed in the next step. This is exposure for processing the portion to be measured for film thickness, as explained in FIGS. 5(A) and 5(B), in order to control the resist film thickness in the next step. The substrate 1 is then labeled 8
At step 5, the sheet is placed on a pot plate 1-73, and after being haked, it is further conveyed at step 87 to an exposure machine where it is needed.

As described above, in this embodiment, in particular, by measuring the film thickness before and after coating, it is possible to control the resist film thickness with very high precision. In addition, film thickness can be controlled by controlling the exposure time as described above, and as a result, line width (processing dimension) control with extremely high reproducibility can be realized.

As described in detail in Section 2, in this example, the film thickness of the underlying thin film or the film thickness of the underlying thin film and the resist film thickness was measured before and after resist application, and the film thickness data obtained before the application was used. By controlling the spin code conditions, it is possible to coat a photoresist film with an appropriate thickness.

Moreover, in this embodiment, more specifically, means for making the film thickness measurement section have the same structure as the actual control part, such as wafer position alignment, UV exposure, and an XY movement stage, are provided. As a result, it is possible to more precisely form a resist film having an appropriate thickness.

In addition, in this example, as described above, the substrate (wafer) after coating is
By measuring the total thickness of the thin film and resist, it is possible to modify the control of the exposure conditions of the exposure machine and the control of the spin code conditions based on the measured total thickness of the thin film and the resist, thereby realizing more precise line width control.

As described above, according to this embodiment, it is possible to realize a precision amplifier for controlling processing dimensions and line widths in photolithography. Therefore, in order to control line widths beyond half a micron in the future, it will be necessary to set detailed lithography conditions for each substrate (wafer). It can be said that it is something that can be realized precisely.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to always apply photoresist at an appropriate film thickness, thereby achieving resist application without variation in film thickness, and thereby realizing processing without variation in processing dimensions or line width. It is something. Furthermore, by knowing the amount of variation in the resist film thickness in advance, it is possible to control the exposure amount during exposure and suppress the variation.

■...Substrate (wafer), 2...Photoresist, 3
3L 32...Thin film, 4...Exposure machine.

■...Film thickness information detection, ■...Film thickness data.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing the operating procedure of an embodiment of the present invention. FIG. 2 is a plan view showing the resist-coated surface of the substrate to be processed. FIG. 3 is a configuration diagram of the film thickness information detection section. FIG. 4 shows an example of the structure of a substrate to which a resist is to be applied. FIG. 4(a) is an example in which there is no base thin film, and FIG. 4(b) is an example in which a base thin film is present. Figure 5 (
A) and (B) are diagrams for explaining processing for measuring film thickness measurement points. FIG. 6 is a diagram showing an algorithm for determining the rotation speed during resist application. FIG. 7 is a diagram showing an example of the configuration of an apparatus for resist coating means. FIG. 8 is a diagram showing the problem, and is a graph showing the relationship between resist film thickness and sensitivity.

Claims (1)

[Claims] 1. In a resist coating means for coating a photoresist on a substrate, detecting information regarding the thickness of a thin film on the substrate to which the photoresist is to be coated, and based on this, determining the thickness of the photoresist to be coated. A photoresist coating means configured to determine an appropriate coating thickness and apply the photoresist at the appropriate coating thickness. 2. Detection of the information regarding the thickness of the thin film is performed in a non-patterned part of the substrate, and the information detected part is made in advance into a structure similar to the processed part where the pattern is to be formed by an exposure machine. Item 1. Photoresist coating means according to item 1.