JPH10106930A - Resist film, its forming method and resist solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient degree of resolution by a method in which the orientation and the attitude of a number of resist molecules, constituting a resist film, are made uniform. SOLUTION: Electrodes A and B are provided on one end and on the other end of the surface of the resist 11 on a wafer 13, and the second pair of electrodes C and D are formed on the surface in parallel with the surface of the wafer 13. Then, a DC current is allowed to flow between the electrodes A and B, and subsequently, a DC current is allowed to flow between the electrodes C and D. Electric field is applied from biaxial direction between the electrodes A and B, and C and D simultaneously or alternately while current value, voltage and current application item are being changed delicately. Subsequently, the wafer is dried up at 100 deg.C, for example. Accordingly, the photosensitive functional group in a resist molecule 15a can be fixed facing to the expected surface to be exposed in the state in which the attitude of each resist molecule is being controlled. A pattern is formed on the fixed resist film 12, and a UV exposing operation is conducted from above a mask 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist film, a method for forming the resist film, and a resist solution.

[0002]

2. Description of the Related Art In recent years, device dimensions in semiconductor devices have been reduced, and in the photolithography process, which is one of the manufacturing processes, fine processing, that is, a processing technique of quarter micron or less is required in the future. is there. Literature (Literature: Journal of Photopolymer Sc
ience and Technology .Volume 7, Number 3 (1994) pp.
433-448, Environmentally Stable Chemical Amplifica
tion Positive Resist; Principle, Chemistry, Contamin
ation Resistance, and Lithographic Feasibility.Hiro
According to shi ITO et al.), ESCAP resist (Environmentally Stable Chemical Amplification) is a resist that has been successfully subjected to lithography using a KrF excimer laser stepper at 0.25 μm (quarter micron).
There was a resist called Positive Resist). However,
The resist film formed by these resists is applied on a wafer and the film thickness is controlled only by a spin coating method or the like. In particular, the orientation and three-dimensional position of the resist molecules in the resist film are controlled. Not
The resist molecules were almost randomly present in the resist film.

[0003] This will be briefly described with reference to the drawings. FIG. 7 is an image diagram of a resist film applied on a wafer, schematically showing a conventional method of forming a resist film. (A)
In the figure, a resist film 52 is formed on a wafer 53, and a mask 57 having a shape corresponding to a desired pattern is formed on the resist film 52.
Is a structural cross-sectional view at the time when the exposure processing is completed.
FIG. 6B is a plan image diagram when the state of the resist molecules 55 in the resist film 52 at the same time as FIG. Exposed portion (exposed surface) 5
The insolubilized resist molecule 55b indicates that the resist molecule 55a of No. 9 is altered and is insoluble in the developing solution.
FIG. 3C is a cross-sectional view of the structure at the time when the lithography process is completed. In this case, a negative resist is used,
(A) The resist film 52 on the exposed surface 59 in the figure remains. Insolubilized resist molecules 55b in the resist film 52
(D) is shown in FIG. Since the resist molecules 55 are present in the resist film 52 in a random state, the resist film 52 after the exposure and the development is uneven due to the influence of the position and orientation of the resist molecules.

[0004]

Generally, it is considered that tens to hundreds of resist molecules having a molecular weight of several thousand to several hundred thousand exist irregularly in a width of, for example, 0.25 μm. Therefore, when processing to a finer line width of quarter micron or less required for the resist, the influence of the position and orientation of the resist molecules becomes greater, so that ultraviolet rays with a short wavelength, electron beams, X-rays, etc. Even if it is used for processing, it is inevitable that the resist cross-section becomes rough and rough after development, and therefore, a sufficient resolution cannot be obtained.

For this reason, there has been a demand for the emergence of a resist film and a method for forming the same that can obtain a sufficient resolution in a fine lithography process.

[0006]

For this reason, the resist film of the present invention is composed of a large number of resist molecules, and the plurality of resist molecules have the same orientation and orientation.

For this reason, since a photosensitive functional group can be directed to the surface of the resist film to be exposed in a photolithographic processing step performed later, the cross section of the processed resist as a result of the lithographic processing of the resist film is obtained. Smooth and sufficient resolution can be obtained.

In the above resist film, the positions of the resist molecules are further aligned. For this reason, the resist cross section after the lithography processing becomes smooth, and the resolution can be further improved.

In the above-mentioned method of forming a resist film, an electric field is applied to a resist solution applied on a wafer in two axial directions to align a large number of resist molecules in the resist solution with their orientations and postures. After that, these resist molecules are fixed.

By applying an electric field simultaneously or alternately from the two axial directions, the respective resist molecules in the resist solution are subjected to an electrophoretic action, and are oriented in the same posture and in a fixed direction. For this reason, in the resist film obtained by fixing the resist molecules in this state, the functional groups that react with the light of the respective resist molecules are directed to the exposed surface of the resist film at the time of exposure in a photolithography process performed later. Can be made to react almost all the resist molecules in the exposed part, and as a result of development,
In the case of a positive resist, the exposed portion can be removed according to a pattern (in the case of a negative resist, the exposed portion can be left as a pattern). Therefore, even in fine processing, the resist cross section becomes smooth,
Resolution can be improved.

In the method of forming a resist film, an x-axis which is a straight line passing through the center of the wafer and passes through the center of the wafer and a y-axis which is a straight line passing through the center and perpendicular to the wafer surface is used. And two axes.

As described above, taking the two axes, the orientation and the attitude of the resist molecules are controlled by the electric field in the two axes of the x-axis direction and the y-axis direction. Explaining the resist molecule as a human hand, first, when an electric field is applied in the x-axis direction, it is assumed that the fingertip is directed in a certain direction. In the uniaxial direction, the directions in which the fingertips are oriented are aligned, but some palms are facing up, while others are facing down. Next, when an electric field is applied in the y-axis direction, the palms can be simultaneously turned upward. When the resist molecules are controlled by applying an electric field in two axial directions in this manner, the posture of each molecule can be controlled. Therefore, the photosensitive functional groups of the resist molecules can be oriented toward the exposed surface.

The resist film applies an electric field to the resist solution applied on the wafer in three axial directions, aligns the orientation, posture and position of the resist molecules, and fixes a number of these resist molecules. I do.

As described above, by applying a biaxial electric field to the resist solution, the attitude of the resist molecules can be controlled. Further, by applying an electric field from another direction, the arrangement of the resist molecules vertically and horizontally, that is, the arrangement position can be controlled.
As a result, the resist cross section after the exposure and development processing can be formed more smoothly, and the resolution can be further improved.

In the method of forming a resist film,
The axis passes through the center of the wafer, the x-axis which is a straight line in the plane of the wafer, the center of the wafer, the y-axis which is a straight line perpendicular to the wafer plane, and the straight line which is orthogonal to the x-axis and the y-axis. And three axes, that is, the z axis.

As described above, the electric field is applied in three directions of the x-axis, the y-axis, and the z-axis by taking three axes, thereby controlling the orientation, posture, and position of the resist molecules.

As described above, when the resist molecules are compared to a human hand, the palm of the hand is directed upward, and each finger is directed in a fixed direction (each hand is controlled by an electric field in two axial directions). Resist molecules) exist at various positions in the space. Therefore, when an electric field is applied from another direction, the position in the space can be determined while the orientation and attitude are controlled. By exposing and developing the resist film thus formed in a certain pattern, the remaining resist cross section becomes smoother, and further improvement in resolution can be expected.

When an electric field is applied in two axial directions in forming a resist film on the wafer, the method of forming the resist film includes a step of applying a resist solution on the wafer,
Providing a first pair of electrodes for the x-axis direction on the surface of the resist solution with the wafer interposed therebetween; and upper and lower surfaces parallel and spatially separated from the resist surface with the surface of the resist solution interposed therebetween A step of providing a second pair of electrodes for the y-axis direction, and a step of applying a direct current to the electrodes for the x-axis direction and the electrodes for the y-axis direction simultaneously or alternately.
Drying the wafer to which the resist solution has been applied.

According to this method, not only is the functional group portion of the resist molecule directed in a specific direction, but also the two pairs of electrodes are energized simultaneously or alternately, whereby the resist molecule is delicately moved and the posture is changed. You can control.

A method of forming a resist film when an electric field is applied from three axial directions includes a step of applying a resist solution on a wafer and a first pair of x-axis directions on the surface of the resist solution with the wafer interposed therebetween. Providing a second pair of electrodes for the y-axis direction on upper and lower surfaces parallel to and spatially separated from the resist surface with the surface of the resist solution interposed therebetween; Providing a third pair of electrodes for the z-axis direction across the wafer on the resist surface in a direction perpendicular to the x-axis direction; The method includes a step of applying a direct current to the electrode and the electrode for the z-axis direction simultaneously or alternately, and a step of drying the wafer on which the resist solution is applied.

This makes it possible to move the resist molecules whose attitude has been controlled, and to align the positions in the resist film.

It is also conceivable that some resist molecules are almost neutral as a whole and are difficult to move even when an electric field is applied. Therefore, in the present invention, an electrolyte is added to the resist molecules in the resist solution.

The added electrolyte has a positive or negative charge in the resist solution and has a function of assisting the movement of the resist molecules. If an electric field is applied to the resist solution applied to the wafer from the biaxial or triaxial directions after the electrolyte is added to the resist molecules, the orientation, posture, and position of the resist molecules that are difficult to move can be controlled. Becomes possible.

The above-mentioned electrolyte is an oligopeptide. Thereby, the electrophoretic movement of the resist molecules can be promoted without hindering the function as the resist film.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of a resist film according to the present invention will be described below. In addition, each figure is only schematically shown to the extent that the present invention can be understood. Further, in the following description, specific materials and conditions are used, but these materials and conditions are merely examples of preferred embodiments, and therefore, the present invention is not limited thereto.

<First Embodiment> First, a method for forming a resist film according to the present invention will be described with reference to FIGS. 1, 2, 3 and 5.
This will be described with reference to FIG. FIGS. 1 and 2 are a sectional view schematically showing steps which are the features of the present invention, and a plan image showing the state of resist molecules in a resist film in each step. FIGS. 3 and 5 are schematic structural views of an apparatus for forming a resist film according to the present invention.

In the present invention, first, L is used as a resist solution.
MR (Low Molecular Weight Resist)
: A naphthoquinone sialic acid sulfonate of cressole type novolac, hereinafter simply referred to as a resist. ) 11 is dropped on a 3 inch wafer (1 inch is about 2.54 cm) 13 and 200
Spin coating at 0 rpm (rotation speed per minute) for 30 minutes (Fig. 1
(A)). FIG. 3B shows the state of the resist molecules 15a in the resist 11 at this time.

Next, electrodes are attached to the surface of the resist 11 on the wafer 13 (see FIG. 3). When the orientation flat (orientation flat) of the wafer 13 is lowered, one end of a straight line extending in the right and left direction (here, this straight line is referred to as x-axis) passing through the center of the wafer 13 and electrodes A and B are provided at the other end. Install (Fig. 3). Preferably, the first pair of electrodes A and B are each arranged in a manner as shown in FIG. That is, the buffer solution 23 is placed in the container 21 in which the electrode 25 is provided at the bottom, and a filter paper-like substance 27 is provided to connect the resist 11 from the container 21. The buffer solution 23 has penetrated into the filter paper-like substance 27, and an electric current flows to the resist 11 through the filter paper-like substance 27. Therefore, electrode A or B is connected to buffer solution 2
3, the electrode 25, and the filter paper-like substance 27.

Next, a second pair of electrodes is formed on a surface parallel to the surface of the wafer 13 (upper and lower surfaces). Here, the upper electrode is C, and the lower electrode is D (FIG. 3).
These second pair of electrodes C and D are provided on the y-axis, which passes through the center of the wafer 13 and is perpendicular to the wafer surface and orthogonal to the x-axis.

Next, for example, 100
V, a DC current of 20 mA is passed. The energization time is set arbitrarily. Thereafter, a direct current is applied between the electrodes C and D.
At the same time, between the electrodes A and B and between the electrodes C and D,
Alternatively, an electric field is applied to the resist 11 from two directions while the current value, the voltage, and the energizing time are changed slightly.
Here, conditions such as a current value, a voltage, and a conduction time vary depending on the size of the wafer, the type of the resist, the solvent, and the like. Therefore, it is necessary to perform an experiment and change the conditions each time.

Thereafter, the wafer is dried at 100 ° C. using a hot plate or an oven. This allows the photosensitive functional groups in the resist molecules 15a to be fixed facing the surface to be exposed, while controlling the attitude of each resist molecule 15a. FIG.
FIG. 3C is an image diagram showing a state of a resist molecule whose orientation and posture are controlled in the resist film 12. The resist film 12 was obtained by fixing the resist 11 on the wafer 13 by a drying process.

Next, after a mask 17 corresponding to the pattern to be formed on the resist film 12 is provided, light energy irradiation of 20 mJ / cm ² is performed from above the mask 17 by a UV exposure machine (FIG. 2). (A)). Thereafter, development processing is performed with chlorobenzene for 30 seconds, and rinsing with cyclohexane for 30 seconds. Then use a hot plate for 100
C. Dry for 2 minutes. Referring to FIGS. 2A and 2B, if a portion where the resist film 12 is not covered with the mask 17 is a surface to be exposed 19, after exposure, the resist molecules on the surface to be exposed 19 are degraded, and are exposed to a developing solution. Insoluble (Fig. 2
(B)). In the figure, the insolubilized resist molecules are indicated by 15b.
Next, when development is performed, a resist film 12 having a pattern as shown in FIG. 2C is obtained, and the insolubilized resist molecules 15b in the resist film 12 at this time are considered to be in a state as shown in FIG. Can be Since the orientation and posture of the resist molecules 15a and the insolubilized resist 15b are controlled (FIG. 1C), the cross section of the resist film becomes smooth after the fine lithography process, and as a result, the 0.2
0 μmL / S (line and space) was successfully resolved.

<Second Embodiment> As a second embodiment, an example in which an electric field is applied to a resist solution on a wafer from three axial directions will be described with reference to FIG.

In the same manner as in the first embodiment, the resist 11 is dropped on the 3-inch wafer 13 and spin-coated, and the first pair of electrodes A and B and the wafer 1 are formed on the surface of the resist 11.
A second pair of electrodes C and D is formed above and behind 3. Thereafter, a straight line that intersects at right angles at the center of wafer 13 with a straight line connecting electrodes A and B on the surface of resist 11 is formed on wafer 1.
3 (resist surface), the third pair of electrodes E, F
Is installed (FIG. 4). These third pairs of electrodes E and F are:
Z passing through the center of the wafer 13 and orthogonal to the x-axis and the y-axis
Provided on the shaft.

Next, a direct current is sequentially or simultaneously applied between the electrodes A and B, between the electrodes C and D, and between the electrodes E and F, and the electric field is changed to align and move the resist molecules. Thereby, the functional group of the resist molecule can be directed to the exposed surface when performing the exposure processing to be performed later. Next, the wafer to which the resist has been applied is dried by heating at 100 ° C. using a hot plate or an oven. as a result,
The photosensitive functional group in the resist molecule can be fixed while facing the surface to be exposed, and the position of the molecule can be controlled.

Next, in the same manner as in the first embodiment, when a mask corresponding to a desired pattern is provided on the resist film and exposure and development are performed, a pattern with higher resolution can be obtained.

Third Embodiment As a third embodiment, an example in which an electrolyte is added to a resist molecule will be described with reference to FIGS. 6A and 6B. FIG. 6 is a plan view showing the state of the resist molecules in the resist.

Depending on the type of the resist molecule 31, the structure may be bent because of a polymer, and a group having a charge may be located inside the resist molecule, making it difficult to perform an electrophoretic operation. is there. Such a state of the resist molecules 31 is shown in FIG. For this reason, for example, an electrolyte 33 such as an oligopeptide is added to the resist molecule 31 and the pH of the solvent is further changed. Orientation, posture, and position of the object can be controlled.

[0039]

The resist film thus obtained is
Since the orientation and posture of the resist molecules in the film are controlled, fine lithography is performed using this resist film, and as a result, the processed cross section of the resist film becomes flat and smooth. Therefore, sufficient resolution can be obtained even in fine processing of quarter micron or less.

Further, as described above, after applying an electric field to the resist solution applied to the wafer from the biaxial or triaxial directions, the resist molecules in the resist solution are fixed to form a resist film. The orientation, posture, and position of the resist molecules in the resist film can be controlled. In other words, since it becomes possible to direct the photosensitive functional group of each resist molecule to the surface to be exposed at the time of exposure in the photolithography process to be performed later, almost all the resist molecules in the exposed portion react and develop, Sufficient resolution can be obtained.

In addition, if an electrolyte is added to the resist molecules in the resist solution applied to the wafer, the electrolyte is charged in the resist solution and electrophoresis of the resist molecules when an electric field is applied. Can help (prompt) a typical movement (movement). Therefore, it is possible to control the orientation, posture, and position of resist molecules that are difficult to move.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional process view for explaining a method of forming a resist film of the present invention, and FIGS. 1B and 1C are image diagrams of resist molecules.

2 (A) and 2 (C) are schematic sectional views for explaining a method of forming a resist film subsequent to FIG. 1 (A), and FIGS. 2 (B) and 2 (D) show resist molecules. FIG.

FIG. 3 is a schematic structural model diagram for describing a first embodiment;

FIG. 4 is a schematic structural model diagram for explaining a second embodiment;

FIG. 5 is a schematic diagram for explaining a method of installing electrodes of the first and second embodiments.

FIG. 6 is an image diagram of resist molecules used for explaining a third embodiment.

FIGS. 7A and 7C are schematic process cross-sectional views for explaining the prior art, and FIGS. 7B and 7D are
It is an image figure of a resist molecule.

[Explanation of symbols]

 11: Resist (resist solution, LMR) 12, 52: Resist film 13, 53: Wafer 15a, 55a: Resist molecule 15b, 55b: Insolubilized resist molecule 17, 57: Mask 19, 59: Surface to be exposed 21: Container 23: Buffer solution 25: Electrode 27: Filter paper-like substance 31: Resistive resist molecule 33: Electrolyte (oligopeptide)

Claims (10)

[Claims] 1. A resist film comprising a large number of resist molecules, wherein the plurality of resist molecules have the same orientation and posture. 2. The resist film according to claim 1, wherein the positions of the plurality of resist molecules are aligned. 3. A resist solution applied on a wafer is subjected to an electric field from two axial directions, and the orientation and orientation of a large number of resist molecules in the resist solution are aligned, and then the large number of resist molecules are fixed. A method of forming a resist film. 4. The method of forming a resist film according to claim 3, wherein the two axes pass through the center of the wafer, an x-axis which is a straight line in the wafer plane, and the center passes through the center, and the wafer surface passes through the center. And a y-axis which is a straight line perpendicular to the axis. 5. An electric field is applied to the resist solution applied on the wafer from three axial directions, and after aligning the orientation, posture, and position of the plurality of resist molecules in the resist solution, the resist molecules are removed. A method for forming a resist film, comprising fixing. 6. The method of forming a resist film according to claim 5, wherein the three axes pass through the center of the wafer, an x-axis which is a straight line in the wafer plane, and the center passes through the center, and the wafer surface passes through the center. 3. A method of forming a resist film, comprising three axes: a y-axis which is a straight line perpendicular to the axis and a z-axis which is a straight line orthogonal to the x-axis and the y-axis. 7. A step of applying a resist solution on the wafer when forming a resist film on the wafer, and providing a first pair of electrodes in the x-axis direction on the surface of the resist solution with the wafer interposed therebetween. A step of providing a second pair of electrodes for the y-axis direction on upper and lower surfaces parallel and spatially separated from the resist surface with the resist solution surface interposed therebetween; And applying a DC current to the y-axis direction electrode simultaneously or alternately, and drying the wafer coated with the resist solution. 8. A step of applying a resist solution on the wafer for forming a resist film on the wafer, and providing a first pair of electrodes in the x-axis direction on the surface of the resist solution with the wafer interposed therebetween. A step of providing a second pair of electrodes for the y-axis direction on upper and lower surfaces parallel to and spatially separated from the resist solution surface with the resist solution surface interposed therebetween; Providing a third pair of electrodes for the z-axis direction on the resist solution surface in a direction orthogonal to each other with the wafer interposed therebetween, the electrodes for the x-axis direction, and the electrodes for the y-axis direction; A method for forming a resist film, comprising: simultaneously or sequentially applying a DC current to an electrode for the z-axis direction; and drying a wafer coated with the resist solution. 9. A resist solution, wherein an electrolyte is added to resist molecules in the resist solution. 10. The resist solution according to claim 9, wherein the electrolyte is an oligopeptide.