JP3225722B2 - Method of forming photosensitive layer for pattern exposure and method of forming pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor circuit, and
The present invention relates to a semiconductor circuit having a line width of sub-half micron or less, and particularly to a method for forming a photosensitive layer for pattern exposure necessary for manufacturing a semiconductor circuit having a relatively large pattern step, and a method for forming the photosensitive layer. And a method of forming a mixed pattern.

[0002]

2. Description of the Related Art In the conventional exposure of a semiconductor wafer having a line width of 0.35 μm, a resist is applied to the wafer by using a spin coater. By applying a resist solution with fluidity to the center of the rotating wafer by this coating, and flowing the resist from the center to the periphery by centrifugal force, a resist of uniform thickness is possible along the wafer surface as much as possible. It has gained. An original image of a circuit pattern on a reticle is projected and exposed on the wafer coated with the resist by using an i-line reduction projection exposure apparatus to form a circuit pattern.

[0003]

As shown in FIG. 7, the surface 211 of the resist 1 applied by the above-described method is used.
As shown in FIG. 221, since the surface of the underlying pattern already formed on the wafer has irregularities, it is applied to the portion of the underlying pattern having minute irregularities close to the size of the minimum circuit pattern. On the other hand, the resist surfaces 211 and 221 have irregularities with a step Δh smaller than the irregularities h ″ of the irregularities of the underlying pattern, whereas, for example, in the case of a memory circuit, the memory cell section and the peripheral circuit section Since the unevenness of the step h occurs over a relatively wide range as shown in FIG. 2, the step h exactly equal to the step h is applied to the resist surface 21 applied here.
It also occurs between 1 and 221.

[0004] Such a step increases in a wafer at the end of a plurality of exposures performed by changing the reticle in a process of manufacturing one semiconductor circuit. However, when the line width of the circuit pattern is larger than the wavelength as in the related art, the circuit pattern is sufficiently resolved above and below the step, even if there is such a large step. No particular problem occurred in the exposure step.

However, as the miniaturization of the semiconductor circuit progresses, the minimum pattern line width w of the circuit becomes smaller than the wavelength λ used for pattern exposure.
It has become about the same. As a result, the range in which the pattern was resolved, that is, the depth of focus DF, was about the same as or less than the step d of the resist. As a result, for example, when focusing on the memory cell section, a phenomenon occurs in which the peripheral circuit section is not resolved, and the yield of the exposure process is greatly reduced.

Such a phenomenon becomes practically impossible to produce in the future when a device having a line width pattern smaller than quarter microns or a device having a large step d is formed. The problem arises.

[0007]

In order to solve the above-mentioned problems, the present invention provides the following means. That is, when a photosensitive layer made of a photosensitive medium such as a resist is formed on an exposed object such as a wafer for forming a semiconductor circuit pattern, an exposed surface on the exposed object and an exposed surface Reference objects having flat surfaces facing each other are arranged at desired intervals, and a photosensitive medium is filled between the two facing surfaces so that a photosensitive layer for pattern exposure is formed. did.

In the case where the photosensitive layer is formed on the uppermost surface, such as a so-called multilayer resist, a medium having a high etching resistance, such as a resist for flattening under the uppermost layer, is used. To form a planarization layer,
The medium having high etching resistance is filled between two opposing surfaces to form a photosensitive layer for pattern exposure. In this case, the uppermost photosensitive layer is usually formed later on the thus formed medium having a high etching resistance.

In order to fill the above-mentioned photosensitive medium or the above-mentioned medium having high etching resistance, the above-mentioned reference object and the above-mentioned object to be exposed are arranged in a clean hermetically sealed container capable of controlling the pressure of the gas inside. Then, the filling between the two opposing surfaces is performed. The specific means for filling the medium is as follows. The sealing before including the medium and placing the two surfaces in opposition to each other, including the medium, and contacting the photosensitive medium or the medium having high etching resistance. The gas pressure P ₁ in the container is filled as described above so that P ₁ <P ₂ with respect to the gas pressure P ₂ in the sealed container when both surfaces are in contact with each other. In addition, the photosensitive medium or the medium having high etching resistance before reaching the filling state is usually in a fluid state.

After the above-mentioned filling state, the photosensitive medium or the medium having high etching resistance is cured. There are various types of curing methods.One method is to make the reference object transparent to light of a desired wavelength, and to irradiate the light of the desired wavelength after reaching the filling state, The photosensitive medium or the medium having high etching resistance is cured. After the photosensitive medium is cured in this way, the photosensitive medium or the medium having high etching resistance is separated from the reference object.

After the above-mentioned medium is filled, in order to perform good peeling if necessary, a photosensitive medium or a medium having a high etching resistance has an adhesive force to the wafer to some extent, Although it is necessary to select a material having viscosity and curing performance, the following means is usually applied in the present invention using the above-mentioned medium material selected based on such criteria.

First, a medium that allows desired atoms or molecules to pass therethrough is used as the reference object. The surface of the reference object other than the portion of the reference object that is in contact with the medium and the desired second portion other than the portion is subjected to a surface treatment for hermetically sealing the desired atoms or molecules. Further, a supply / exhaust means for supplying the desired atom or molecule to the reference object or exhausting the reference atom from the reference object is connected to the second portion.

With such a structure, the desired atoms or molecules are supplied from the supply / exhaust means when the reference object and the photosensitive medium are separated or separated from the contact state. Further, the supply gas pressure P ₃ of the desired atom or molecule is set such that P ₃ > P ₂ ′ with respect to the pressure P ₂ ′ of the gas in the sealed container at the time of the separation or separation. Further, the pressure P ₂ ′ of the gas in the sealed container at the time of peeling or separation is smaller than the pressure P ₂ of the gas in the sealed container at the time of assuming the filled state.
P ₂ ′ <P ₂ is satisfied. The desired atoms or molecules at the time of separation or separation are rare gases such as He or gases having a small molecular diameter such as H ₂ , and the medium through which the desired atoms or molecules pass is made of, for example, quartz glass having high purity. To do.

A semiconductor circuit is manufactured by irradiating an object to be exposed having a photosensitive layer for exposure formed by the method described above on the surface with a particle beam containing light. Although the semiconductor circuit thus manufactured is manufactured by irradiating an electromagnetic wave including light having a wavelength of λ, the pattern has a minimum line width of w, and the pattern of the minimum line width is w. The step between the two formed surfaces is a maximum h, and h ≧ 1.4 w ²
/ Λ is satisfied. In addition, a semiconductor circuit satisfying such a structure is effectively formed by one exposure using one mask or reticle.

Further, in the method for forming a photosensitive layer for pattern exposure according to the present invention, if a semiconductor circuit pattern is drawn on the surface of the reference object having the flat surface facing the object to be exposed, After filling the photosensitive medium, a desired pattern can be formed on the photosensitive medium by exposure simply by irradiating exposure light without using a projection optical system.

Further, in the method for forming a photosensitive layer for pattern exposure according to the present invention, the shape of the surface of the reference object having the flat surface facing the object to be exposed is changed to an image of an image formed by a projection optical system used for exposure. If the surface shape is matched, even if the curvature of field of the projection optical system is large, it is possible to form and expose the surface of the photosensitive medium in the best focus state.

[0017]

A photosensitive medium or a medium having high etching resistance is filled between two opposing surfaces, so that the surface on the surface of the object to be exposed, such as a wafer, does not depend on the unevenness of the surface of the object to be exposed, such as a wafer. The uppermost surface of the photosensitive medium or the medium having high etching resistance, that is, the surface not in contact with the surface of the object to be exposed such as a wafer, is flat because it follows the surface of the reference object. As a result, if a circuit pattern is image-formed or projected on this flat surface, the circuit pattern can be formed on the photosensitive layer surface even if the depth of focus DF is smaller than the step d of the underlying pattern. Can be formed.

By forming such a photosensitive layer having a flat top surface by the method under the above-mentioned pressure conditions,
The photosensitive medium or the medium having a high etching resistance has good adhesion to the surface of the object to be exposed without forming so-called bubbles, and forms an uppermost surface shape following the flatness of the reference surface. It becomes possible.

That is, if the pressure P ₁ of the gas in the sealed container immediately before filling between the two surfaces is sufficiently low, for example, a state close to a vacuum, no bubbles are generated after filling. Further, even if it is not a vacuum, even if the filling medium contains a solvent, the gas pressure P
If there is almost no gas of molecules other than the solvent to the extent that ₁ is almost equal to the partial pressure of the solvent, no bubbles will be generated after filling. It is necessary that the pressure P ₁ immediately before the filling is smaller than the pressure P ₂ in the contact state after the filling,
The smaller the size, the less bubbles are generated.

After the filling state, the photosensitive medium or the medium having high etching resistance is hardened. There are various types of curing methods.One method is to make the reference object transparent to light of a desired wavelength, and to irradiate the light of the desired wavelength after reaching the filling state, The photosensitive medium or the medium having high etching resistance is cured. By curing as described above, the pattern is not locally distorted after the pattern is formed.

After the photosensitive medium is cured as described above, when a circuit pattern is drawn on the reference object, the reference object on which the circuit pattern is drawn is peeled off. If the exposure light is irradiated while the photosensitive medium is filled, the circuit pattern drawn on the reference object can be exposed on the photosensitive medium with high resolution.

When a circuit pattern is not drawn on the reference object, the photosensitive object or the medium having high etching resistance is generally separated from the reference object. The top surface of a photosensitive medium or a medium with high etching resistance after peeling has a shape following the reference object surface, so even if there is a large step on the wafer surface, images are formed with electromagnetic waves including light. Fine pattern using optical system
Can be exposed at a high resolution.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

FIG. 1 is a view showing a method of forming a photosensitive layer for pattern exposure according to the present invention, wherein 1 is a photosensitive medium and 1 'is a medium having high etching resistance. An initially fluid photosensitive medium or a medium 1 or 1 'having high etching resistance is supplied to the surface to be exposed on the object to be exposed 2, and the reference object 3 having a flat surface opposed to the surface to be exposed is provided. The photosensitive medium is filled between the two surfaces so that the space between the two surfaces is a desired distance.

When the filled photosensitive medium 1 or the medium 1 ′ having high etching resistance and the reference object 3 are separated (released) by a method described later, as shown in FIG. A photosensitive medium 1 having a flat top surface or a medium 1 'having high etching resistance is formed on the object to be exposed. When using a medium 1 'having high etching resistance,
On this medium, as shown in FIG.
Is formed by coating, vapor deposition or sputtering. The wafer on which the photosensitive layer is formed is carried into an exposure apparatus such as a reduction exposure apparatus (not shown), and a pattern of a mask or a reticle is overlaid on the photosensitive layer and exposed.

FIG. 2 shows an embodiment of a method for forming a photosensitive layer for pattern exposure according to the present invention and a semiconductor circuit using the same. In the reference object 3 ′, a circuit pattern 31 is drawn on a surface facing the wafer 2 having unevenness. As shown in the embodiment of FIG. 1, the resist supplied on the upper surface of the wafer 2 is
With the circuit pattern surface 31 and the pattern surface of the wafer kept at a desired distance, the space is filled within the desired distance, and then the exposure light 5 'is irradiated. Before or after this exposure, the filled resist is cured by applying light or heat to which the resist is not exposed.

After the exposure and curing are completed, when the reference object is peeled off, as shown by a dotted line in FIG. 2B, the surface of the resist on the wafer is flat and the circuit pattern has already been exposed. 2 (c) by developing.
As shown in (1), even if there is a step at the portions 21 and 22, a circuit pattern of the resist is formed in a sharp form, and a pattern having a high resolution can be formed by etching performed thereafter.

FIG. 2D shows a method of forming a photosensitive layer for pattern exposure described with reference to FIG. 1 or FIG. 2 and a cross-sectional structure of a semiconductor circuit manufactured by this method. For example, in the case of a semiconductor memory circuit, the pattern 211 of the memory section is higher than the pattern 221 of the peripheral circuit section by h, so that the base pattern of the peripheral circuit section is practically effective. H ′ is higher in the highest part of the memory cell portion than the memory cell.

When a conventional resist coating method is used, the difference in the height of the resist surface is h 'to h. Even when such a wafer is exposed using a conventional semiconductor exposure apparatus, assuming that the exposure wavelength is λ and the minimum dimension of the exposure pattern is w, the depth of focus DF of the exposure optical system is given by Expression 1. Under the condition (1), a pattern cannot be formed.

[0030]

(Equation 1)

Condition 1: Exposure without using a phase shift reticle In this case, Equation 1 is established, and the width of focus is 2D.
Where F is an allowable value of h or h ′ in consideration of the focus detection / control accuracy L of the exposure apparatus, the flatness F in the exposure area of the wafer, the curvature C of the image forming surface of the projection optical system, and the like. Is given by Equation 2.

[0032]

(Equation 2)

If the exposure wavelength is i-line (λ = 0.365 nm) and the pattern width w is 0.5 μm, DF = ±
0.95 μm, L = ± 0.1 μm, F = 0.4 μm
Assuming that m and C = 0.4 μm, h ≦ 0.
9 μm. When the exposure wavelength is KrF excimer laser (λ =
0.248 nm), the pattern width is w = 0.35 μm.
If m, DF = ± 0.69 μm, and from Expression 2, h ≦ 0.4 μm.

Condition 2: Exposure using a phase shift reticle

[0035]

(Equation 3)

In this case, the equation of the depth of focus DF 'is the above-mentioned equation (3). The exposure wavelength is i-line (λ = 0.365 nm),
Assuming that the pattern width is w = 0.35 μm, DF = ±
0.75 μm, L = ± 0.1 μm, F = 0.4 μm
Assuming that m and C = 0.4 μm, h ≦ 0.
5 μm. When the exposure wavelength is KrF excimer laser (λ =
0.248 nm) and the pattern width is w = 0.25
Assuming μm, DF = ± 0.53 μm, and from Expression 2, h ≦ 0.1 μm.

As can be seen from the above example, when a sub-half micron (finer than 0.5 μm) pattern is to be exposed, the circuit pattern is exposed if h ≦ 1.4 w ² / λ is not satisfied. You can't do that. In other words, conversely, by using the method for forming a photosensitive layer for pattern exposure according to the present invention, the pattern step h of the wafer (or the effective pattern step h ′) is h ≧ 1.4 w ^{2 for the first time.} A semiconductor circuit satisfying / λ can be formed.

FIG. 3 shows an embodiment of a method for forming a photosensitive layer for pattern exposure according to the present invention and a method for exposing a circuit pattern on the photosensitive layer for pattern exposure using a reducing lens by this method.
As emphasized in FIG. 3B, the image plane of the reduction lens is curved, not flat. Therefore, even if the wafer surface is flat in the exposure shot area, if the best focus surface is curved, as described in the previous embodiment,
This effectively lowers the depth of focus. Therefore, in this embodiment, the shape 13 of the surface 32 of the reference object 3 ″ facing the wafer
2 is adjusted to the shape 632 of the field curvature of the exposure apparatus.

In this way, even if there is a field curvature, even if the pattern of the normally used flat reticle 4 is projected and exposed by the reduction lens 6, the image forming surface 632 remains on the resist surface 132. In principle, exposure can be performed in the best focus state over the entire exposure area.

FIG. 4 shows a more specific method of forming a photosensitive layer for pattern exposure in an embodiment of the present invention. 70 is clear
Is a simple sealed container (chamber), and a space 71 inside the container.
Is measured by the pressure gauge 74, and the pressure control system 7
2 and the valve 721 are controlled. Further, desired gas molecules 84 are introduced into the sealed container through an inlet 841 in order to fill the gas molecules 84 with a desired partial pressure. A passage 73 for loading and unloading wafers into and from this sealed container is provided with a gate valve 731.
Is installed through. The wafer supplied from the outside of the sealed container into the container through the gate valve supplies a desired amount of resist to the surface of the wafer to a certain extent by the resist supply device 83 in accordance with the surface unevenness of the wafer. Since the supplied resist is low in viscosity and rich in fluidity, the resist is uniformly spread on the wafer and almost to the final resist thickness with the help of the wafer driving mechanism 82.

The flow of FIG. 6 - Cha - as shown in bets, the pressure P in the sealed container is left in the P ₁ closer to the vacuum at this time. However, this pressure is determined in consideration of the volatility of the solvent dissolved in the resist, and if necessary, the gas of the solvent is introduced into the inlet 841 so as to have a desired partial pressure P ₁ ′ in order to control the volatilization. Supplied from As shown in the flowchart of FIG. 6, the reference object 3 is brought close to the wafer held on the wafer holding mechanism 85 by the reference object holding drive mechanism 81 so that the interval becomes zero, and a slight pressure is applied. The thickness of the resist becomes a desired thickness ΔG, and the resist is filled between both surfaces. The internal pressure P of the sealed container at this stage to larger P ₂ than the pressure P ₁ of the.

Thereafter, light for curing the resist is irradiated from above the reference object to cure the resist, and thereafter the reference object is separated from the resist on the wafer by using the reference object holding / driving mechanism 81. In order to facilitate the peeling, it is preferable to coat the surface of the reference object in contact with the resist with a release agent having a small adhesive force on the resist. Further, if a reference object having a structure as shown in FIG. 8 is used, it can be more easily peeled off.

In FIG. 8, the reference object 3 is made of high purity quartz. Quartz of high purity can be obtained by using He gas or H ₂ gas with a small molecular diameter.
Pass gas well. The portion of the quartz surface that is in contact with the wafer remains the quartz, except for this portion, except for the second portion 303, where the surface is treated so as to prevent the passage of gas having a small diameter of these molecules. deep. In this way 3
A portion 304 is connected to a pipe 304 for supplying a gas having a small diameter of these molecules. When the reference object is stripped from the resist on the wafer in this manner, the pipe 304
Or He or H ₂ gas. The supply gas pressure P ₃ is set to a pressure sufficiently higher than the pressure P ₂ ′ in the sealed container at the time of peeling.

By setting such a pressure relationship and a force other than the gravity of the reference object other than its own gravity to be negligible, the gas can seep out between the closely adhered resist and the reference object and easily peel off. Will be possible. Although the reference object capable of supplying gas shown in FIG. 8 is entirely made of quartz, a path passing through the quartz portion is long in such a structure, and sufficient gas cannot be supplied in a short time.

FIG. 9 shows an embodiment of the present invention, in which a flat base 310 having a high rigidity is cut at the same height and the tip is cut, and a conical spacer 312 whose bottom surface is parallel to the cut surface is provided. A plurality of reference objects having a high degree of parallelism are adhered below the spacer. The space with the spacer is connected to the tube 304. In a state where the medium 1 ′ having high etching resistance is filled on the wafer, ultraviolet light is irradiated through the transparent side wall 311 using the optical fiber 5 ″ to cure the medium 1 ′ having high etching resistance. To make sure that
The surface on the spacer side of the flat base 310 having high rigidity is processed so that ultraviolet rays are irregularly reflected.

Although only one fiber is shown in FIG. 9, a fiber end is arranged around the fiber, and uniform ultraviolet irradiation is performed. He gas is supplied from the tube 304 in order to peel the hardened medium 1 ′ having high etching resistance from the reference object. He
Since the reference object made of quartz that allows the light to pass therethrough is thin, the wafer can be separated from the reference object in a short time. In order to apply a photosensitive substance on the exfoliated flat medium 1 ′ having high etching resistance, a photosensitive layer is formed by using, for example, a spin coater.

FIG. 10 shows an embodiment of the present invention, in which a material having high permeability and high rigidity, for example, a sintered metal 320 is used. The lower surface of the material is flat, and a reference object having air permeability is partially bonded to the flat surface so as to maintain air permeability. The surface other than the adhesive surface is covered with a material 301 having a high sealing property. A tube 304 is connected in the same manner as in FIGS. 8 and 9, and a gas having a small molecular diameter is supplied to remove the resist from the reference object. Peel off.

FIG. 11 shows an embodiment of the present invention. In this embodiment, the strain of the reference object is used as a method for filling and peeling the photosensitive layer or the medium having high etching resistance. FIG.
(A) is a mechanism diagram for realizing this method. The reference object 3 is fixed to the reference object holding mechanism 330 having high rigidity around the reference object 3. A piezo element 331 is provided on the back of this reference object.
Are arranged at substantially equal intervals. One end of the piezo element is fixed to the reference object holding mechanism 330, and the other ends of the piezo element are in contact with each other by pressing the back surface of the reference object. An electric wire for driving the piezo element is wired from inside the reference object holding mechanism 330 to the outside, and is connected to the drive control circuit 333. Each piezo element is driven by the drive control circuit 333 so that the reference object 3 has a desired shape.

At this time, the photosensitive layer or the medium 1 having high etching resistance accurately comes into contact with the reference object 3, and finally,
This measurement information is transmitted to the drive control circuit 333 while performing the following measurement so that the thickness of the photosensitive layer or the medium having high etching resistance filled between the two objects becomes a desired value as a whole. Then, the driving of the piezo element 331 and the driving of the wafer holding mechanism 85 in the vertical (z) direction are performed using this information.

This measurement includes measurement of the shape of the reference object and measurement of the distance in the z direction between at least one surface of the reference object 3 and the wafer or the holding surface of the wafer holding mechanism. As the latter gap measuring device 334, an optical gap sensor, an air micro sensor, a capacitance sensor, or the like is used in addition to a widely used laser interferometer. Although it is preferable to provide this gap measuring device at three places around the wafer,
If the shape information of the reference object shape measuring device is used, a plurality of measurements are not necessarily required, and only one location may be used.

Next, the former measurement is shown in FIGS.
This will be described with reference to FIG. This measuring method is disclosed in
In this method, the inclination and height of the surface are obtained by using the interference of a laser in a method whose details are shown in FIG. The shape measuring machine is provided at two places, and 337 is the lower surface of the reference object.
47 measures the upper surface of the reference object. 337 or 347
Has a laser light source (not shown), and the laser beam is made to have a desired beam diameter by a beam expander (not shown). This beam is divided into two parts by a beam splitter and a reference object holding mechanism 33 is provided by a shape measuring machine 337 or 347.
The two beams split into the reference object are made to enter the reference object from the window on the side of 0 (also a part holding the side surface of the reference object).

The light emitted from the shape measuring device 337 advances in the x direction, and the light emitted from the shape measuring device 347 advances in the y direction.
Shape measurement device 337 2 minutes have been 2 Tsunobi emitted from - beam is wider in the y direction shown in FIG. 11, the width is w _y,
narrow in the z direction and the width is w _z. w _y is approximately equal to the wafer diameter D _w , w _z is the angle of incidence on the lower surface of the reference object plane θ
Then, w _z = D _w / cos θ.

A measurement method using this interference will be described with reference to FIG. One of the two divided lights is the object to be measured (FIG. 12).
O, the object light (or measurement light) 338 or 34 applied to the lower or upper surface of the reference object 3 in FIG.
8 and the other light is used as interference reference light 339 or 349. After the object light is reflected by the measured object O, the reflected mirror M or 3371 or 34
The light that is perpendicularly incident on 71 and is specularly reflected returns to its original path.

The two lights are superimposed on the surface indicated by Σ shown in FIG. 12A, and interference fringes are generated. This interference fringe is formed by the imaging lens 3
When an image is formed on the CCD image pickup device 3377 at 36, FIG.
An interference signal as shown in (b) is obtained. A of this interference signal
And B substantially correspond to the A and B portions of the object O. Since the phase of this interference fringe indicates the height of the object to be measured, the phase of the interference fringe shown in FIG.
The shape of the surface of the object to be measured in (c) can be obtained.
Although only one interference signal is shown in FIG.
Since 3377 (or 3377) can perform two-dimensional imaging, this interference fringe signal is obtained over the entire reference object. The obtained signal is processed by the height measurement processing circuit 300 to measure the height of the entire reference object, that is, the surface shape.

As shown in FIGS. 11B and 11C,
The lower and upper surfaces of the reference object are measured separately and independently. The purpose is to measure the shape of the lower surface, but when the reference object comes into contact with a photosensitive object on the wafer or an etching-resistant medium, there is almost no reflection on the surface of the reference object,
Reflection from the uneven surface of the wafer is mainly involved. Therefore, after the contact, the shape information of the upper surface of the reference object measured by 347 in FIG.
7 supplements the measurement of the contact portion that cannot be measured. Further, the piezo 331 is driven based on the measurement information, and the shape measuring device 337 can detect the moment when the reference object and the resist or the medium having high etching resistance change from the non-contact state to the contact state.

In other words, as shown in FIG. 14A, in the non-contact state, the light is totally reflected on the lower surface of the reference object 3, so that the cross section of the detection light A ₁ A ₂ as shown in FIG. 14 (c), but in a state of contact as shown in FIG. 14 (c), the light passes through the reference object 3 between the contact portions B ₁ 'B ₂ ' and the wafer surface Since the light is irradiated on the unevenness and is scattered here, a portion corresponding to this region corresponds to FIG.
As shown in FIG. 4 (d), the number of detected pieces becomes weak, and it can be seen that the detected pieces are in contact with each other.

Since not only the detected light amount but also the shape measurement result rapidly changes, the moment when the detected light amount or the shape measurement result changes is captured, and the shape information of the reference object and the reference object at this time are captured. By using the information on the distance between the wafer and the wafer holding mechanism, the piezo 33
1 and the vertical movement of the wafer holding mechanism 85 is performed more accurately.
Control the film thickness of the filler to a desired constant value.
It becomes possible to do.

When the filling is completed in this manner, ultraviolet rays are irradiated from above through the reference object to cure the filling material. When the curing is completed, the process is exactly the reverse of that from the non-contact state to the contact state, and the contact state is released (release).

FIG. 13 shows an embodiment of the present invention. A method of performing contact and separation with a reference object using the fact that a wafer is usually thin and easily deformable is shown. In this embodiment, the reference object 3 or the reference object 3 'on which the pattern is drawn is sufficiently thick and rigid. The flat lower surface is contacted with a low-viscosity fluid photosensitive object or an etching-resistant medium applied on the wafer. At this time, the wafer is brought into contact while controlling the shape of the deformed chuck 20. At this time, as shown in FIG. 13A, the control of the deformation chuck and the vertical control of the wafer holding mechanism 85 are performed while monitoring the state of contact.

First, as shown in FIG. 13 (a), each piezo 331 'is controlled so that the deformed chuck is in a convex state. In the state of being convex upward, the extension of each piezo,
It is measured by a means such as a strain gauge 3311 '.

Next, the wafer holding mechanism is gradually raised, and the amount of movement is measured by a length measuring machine (not shown).
Further, the contact surface is constantly monitored by the contact state detection system 35. In the contact state detection system 35, light having high directivity is radiated from the illumination system 352 to the contact area through the side surface of the reference object, and the reflected light is extracted through the side surface of the reference object similarly. The image of the contact area is formed on the imaging surface 351. Because larger the critical angle theta _c incident angle theta of the illumination light to the contact area, the totally reflected by the non-contact state, has exactly the same intensity distribution as the intensity distribution of the uniform illumination light to the imaging device 351. When a photosensitive object or a medium having high etching resistance comes into contact with the photosensitive member, total reflection does not occur at that portion, so that the intensity of the portion is weakened and the contacting portion can be easily detected.

While keeping the height of the contacting portion unchanged, that is, constantly detecting the contact state, the control system 333 'moves the wafer holding mechanism slightly upward based on the detected information. , The amount corresponding to this movement amount,
Reduce the piezo in the contact area. Thus, FIG.
If the photosensitive object or the medium having high etching resistance is completely filled as shown in FIG. Irradiate 5 ′ and expose. The medium 1 ′ having high etching resistance is used, and in the case of the transparent reference object 3, the medium is cured by irradiating ultraviolet rays 5. Thereafter, the wafer is separated from the reference object by following a process opposite to the process that has reached the contact.

In the filling method and the peeling method described with reference to FIGS. 11 and 13, only the deformation of the contact object is used. However, by combining the peeling using the gas shown in FIGS. In addition, the mold can be released without causing surface deformation.

FIG. 15 shows an embodiment of the present invention and shows a method of forming a photosensitive layer for pattern exposure by filling a medium having high etching resistance. First, benzophenone, benzoin isopropyl, and the like, which are curable with respect to ultraviolet light and have high etching resistance, such as 1,6 hexanediol dimethacrylate, 1,10 decanediol dimethacrylate, dicyclopentane diacrylate, and the like. A solution to which a photopolymerization initiator such as ether or Michler's ketone is added is applied by a spin coater 100.

As described above, the wafer on which the medium having high etching resistance, which is still in a fluid state, is loaded into the clean container 70 through the gate valve 731, and the wafer deformation chuck on the wafer vertical drive mechanism 851. 20. The wafer deformation chuck 20 is first held in an undeformed state, and while measuring the surface shape using the shape measuring device 357 whose detection principle has been described with reference to FIG.
As shown in (1), it is deformed into an upwardly convex shape, and this deformed shape is measured.

By this measurement, the unevenness on the wafer, especially the concave portion, can be determined.
By changing the position of the minute amount feeder 83, the medium having the same high etching resistance as that applied in 00 is selectively supplied while controlling the minute amount. Further, since the recessed portion can be known from the design data without using the above-described shape measurement, the position of the small-volume feeder 83 is selectively changed based on the data by changing the position of the very small amount of medium having high etching resistance. A small amount may be supplied under control.

In this manner, the wafer is supplied to such an extent that the recessed portion is filled. At this stage, the wafer up / down driving mechanism 851 is driven to move the wafer upward until it comes into contact with the reference object. At this time, the contact state between the reference object 3 and the medium 1 'having high etching resistance is detected using the contact state detection system 35 described in the embodiment of FIG.

When the contact state is detected first, the drive amount of the wafer up-down drive mechanism 851 and the deformation amount of the deformation chuck are controlled while constantly monitoring the contact state using the contact state detection system 35, and the etching resistance is controlled. Is filled with a uniform thickness. In this process, the pressure of the clean container 70 is reduced as much as possible.

When the medium 1 'is filled by the above-described method, ultraviolet rays are irradiated from the curing ultraviolet light source 50 through the windows 19' and 19 "to cure the medium 1 '. When the curing is completed, the wafer vertical drive mechanism The wafer is peeled from the periphery of the wafer while controlling the driving amount of the wafer 851 and the deformation of the deformable chuck. When the peeling is completed, the wafer is returned to the spin coater 100, and the photosensitive object is coated on a medium having high etching resistance, and the above steps are controlled by the control circuit 355.

After the medium 1 'having high etching resistance is brought into contact with the reference object, a release agent is coated on the surface of the reference object in order to easily peel off the reference object without distortion. For example, CF ₂ = CF ₂ , octafluorocyclobutane as a monomer is used to coat several hundred 膜 of a film by plasma polymerization, or a silicon-based polymer is dissolved in an appropriate solvent and spin-coated.

By doing so, it is possible to cleanly separate from the reference object. However, with very low probability, stripping may not be successful and a very small amount of medium with high etch resistance may remain on the reference object. So Figure 1
The foreign substance monitor 36 in the clean container 5 detects this. It is desirable to perform this detection before filling and after peeling,
It is enough even after peeling.

[0072]

According to the method of forming a photosensitive layer for pattern exposure according to the present invention, the uppermost surface of the photosensitive layer formed thereon becomes flat even on a wafer having a large pattern step, For example, there is a large pattern step generated in the memory cell portion and the peripheral circuit portion of the memory circuit, and even if the difference exceeds the depth of focus of the exposure system, it is possible to perform exposure with a sufficient focus margin.

As a result, a circuit having a line width smaller than 0.5 μm can be produced at a high yield. Especially when trying to form a pattern with a narrower line width using light.
In the past, a circuit having a pattern step larger than 1.4 w ² / λ could not be formed. However, such a restriction of the step was substantially eliminated, and it became very advantageous in pattern design and manufacturing.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, showing a method of forming a photosensitive layer for pattern exposure.

FIG. 2 illustrates a method using a reference object on which a pattern is drawn and a pattern formed by the method according to an embodiment of the present invention.

FIG. 3 is an embodiment of the present invention applied to a reduction lens having a field curvature.

FIG. 4 shows an embodiment of the present invention, showing a method for forming a photosensitive layer for pattern exposure in a clean container capable of controlling pressure.

FIG. 5 is a view showing an embodiment of the present invention, showing a method of forming a layer in a clean container.

FIG. 6 is a diagram showing a flow of the method of the embodiment of FIG. 4;

FIG. 7 shows the surface shape of a wafer and the shape of a photosensitive layer formed by a conventional method.

FIG. 8 shows a method of peeling by holding a scum having a small molecular diameter in the embodiment of the present invention.

FIG. 9 shows a method of peeling off a scum having a small molecular diameter in an embodiment of the present invention.

FIG. 10 shows a method of peeling by holding a scum having a small molecular diameter in the embodiment of the present invention.

FIG. 11 illustrates a method using distortion of a reference object according to an embodiment of the present invention.

FIG. 12 is a view for explaining the surface shape measuring method of FIG. 11;

FIG. 13 shows a method using distortion of an object to be exposed in an embodiment of the present invention.

FIG. 14 is an explanatory diagram of a method for detecting contact with a reference object.

FIG. 15 is a diagram showing a method from application of a medium having etching resistance to formation of a photosensitive layer in an example of the present invention.

[Explanation of symbols]

1 is a photosensitive object such as a resist, 1 'is an object having high etching resistance, 2 is a wafer, 20 is a wafer deformation chuck, 2
1 is a memory cell part, 22 is a peripheral circuit part, 3 is a reference object,
3 'is a reference object on which a pattern is drawn, 4 is a reticle,
5 'and 51 are exposure light, 6 is a reduction lens, and 632 is an image plane. 7 is a clean sealed container, 72 is a pressure control system, 8
1 is a reference object holding drive mechanism, 82 is a wafer drive mechanism, 8
Reference numeral 3 denotes a resist feeder, and reference numeral 84 denotes a desired gas flow.
300 is a height measurement processing circuit, 331 and 331 'are piezo elements, 333 is a drive control circuit, 337 and 347 are shape measurement machines, 355 is a control circuit, 334 is a gap measurement machine,
04 is a gas supply pipe, 320 permeable rigid material, 331
1 'is a strain gauge. Reference numeral 100 denotes an apparatus for applying a medium and a photosensitive layer having high etching resistance.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Watanabe 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Production Technology Laboratory (72) Inventor Yasuhiko Nakayama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (72) Inventor: Masaki Yoshii 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture In-house Hitachi, Ltd. (56) References JP-A-6-275519 (JP, A (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521 H01L 21/3065

Claims (14)

(57) [Claims] 1. A method of forming an image plane of an image formed by a projection exposure optical system used for exposing a surface of a photosensitive layer for pattern exposure of an object to be exposed.
A photosensitive layer for pattern exposure, wherein a flat surface of the photosensitive layer is formed by pressing the flat surface of a reference object having a flat surface that fits and curing the photosensitive layer. Forming method. 2. A shape of an image plane of an image formed by a projection exposure optical system used for exposure by supplying a photosensitive medium onto an exposed surface of an object to be exposed.
A reference object having a flat surface coinciding with the photosensitive medium is disposed such that the flat surface faces the exposed surface at a desired interval with the photosensitive medium interposed therebetween. A pattern exposure is performed by filling between the exposed surface and the flat surface, curing the filled photosensitive medium, and after curing the photosensitive medium, removing the reference object from the surface to be exposed. Forming a photosensitive layer for pattern exposure, comprising forming a photosensitive layer for pattern exposure. 3. The reference object is transparent to exposure light, and a circuit pattern to be exposed is drawn on one surface of the reference object so that the drawing surface and the surface to be exposed on the object to be exposed face each other. The photosensitive layer for pattern exposure is formed by filling a photosensitive medium between the two opposing surfaces to form a photosensitive layer for pattern exposure. Method. 4. A method for forming a photosensitive layer for pattern exposure, comprising: forming a planarizing layer made of a medium having high etching resistance on an exposed object; and forming a photosensitive layer on the planarizing layer. The shape of the image plane of the image formed by the projection exposure optical system used for the exposure on the surface to be exposed on the object to be exposed and the surface to be exposed
A pattern exposure photosensitive layer is formed by filling the medium having high etching resistance between the two opposing surfaces with reference objects having flat surfaces that match each other arranged at a desired interval. A method for forming a photosensitive layer for pattern exposure. 5. The method according to claim 1, wherein the reference object is made of a medium through which desired atoms or molecules can pass. 6. The surface of the reference object other than the portion of the reference object that is in contact with the photosensitive medium or the medium having high etching resistance and the desired second portion other than the portion is the desired atom or the desired atom. 6. The method for forming a photosensitive layer for pattern exposure according to claim 5 , wherein a surface treatment having a sealing property is applied to the molecules. 7. the desired atomic or molecular in the second portion, provided to the reference object or pattern according to claim 6, wherein the connecting the supply and exhaust means for exhausting from said reference object -A method for forming a photosensitive layer for exposure. 8. A pattern according to claim 7, wherein said desired atoms or molecules are supplied from said air supply / exhaust means when said reference object and said photosensitive medium are separated or separated from the contact state. A method for forming a photosensitive layer for exposure. 9. The supply gas pressure P3 of the desired atom or molecule at the time of peeling or separating is P3> P2 'with respect to the gas pressure P2' of the gas inside the sealed container at the time of peeling or separating. 9. The method for forming a photosensitive layer for pattern exposure according to claim 8, wherein 10. The pressure P2 'of the gas in the sealed container at the time of peeling or separating is smaller than the pressure P2 of the gas in the sealed container at the time of the filling state by P2'<
10. The method for forming a photosensitive layer for pattern exposure according to claim 9 , wherein P2 is satisfied. 11. The photosensitive layer for pattern exposure according to claim 5 , wherein said desired atoms or molecules for said separation or separation are rare gases such as He or gases having a small molecular diameter such as H2. Forming method. 12. A medium for passing the desired atoms or molecules is made of quartz glass.
5. The method for forming a photosensitive layer for pattern exposure according to item 5 . 13. A photosensitive medium is supplied onto an exposed surface of an object to be exposed, and a reference object having a flat surface, transmitting exposure light and drawing a light-shielding pattern is used as the reference surface. The photosensitive medium sandwiched between the flat surface and the exposed surface is disposed so as to face the surface to be exposed at a desired interval with the medium therebetween, and the filled photosensitive medium is filled. Exposure light is irradiated from the side of the reference object on which the light-shielding pattern is drawn on the photosensitive medium and cured, and the reference object is peeled off from the surface to be exposed while the photosensitive medium is cured, and the reference object is removed. The peeled photosensitive medium is developed to form a pattern on the photosensitive medium corresponding to the light-shielding pattern, and the exposed object on which the pattern of the photosensitive medium is formed is subjected to an etching process to form a circuit pattern on the exposed object. Forming a pattern Forming method. 14. A photosensitive medium is provided on an exposed surface of an object to be exposed.
The shape of the image plane of the image formed by the projection exposure optical system used for supplying and exposing
A reference object having a flat surface corresponding to the shape
The photosensitive medium is sandwiched at a desired distance from the surface to be exposed across the photosensitive medium.
The photosensitive medium sandwiched between the
Filling between the exposed surface and the flat surface;
Reference object on which the light-shielding pattern is drawn on the exposed photosensitive medium
The photosensitive medium is cured by irradiating it with exposure light from the side of
The reference object is peeled off from the surface to be exposed in the
Then, the photosensitive medium from which the reference object has been peeled off is developed, and
Forming a pattern on the photosensitive medium corresponding to the light pattern ,
Etching the exposed object formed with the pattern of the photosensitive medium
Circuit pattern on the exposed object
Forming a pattern.