JPH08203877A - Pattern formation - Google Patents

Abstract

PURPOSE: To prevent charge up due to electron beam lithography and deterioration of writing due to proximity effect. CONSTITUTION: A field oxide, a gate oxide 12 and polysilicon 13 are deposited on a silicon substrate 11 followed by deposition of microposit photoresist 14. It is then coated with a cyclohexane solution containing poly (di-t- butoxystanoxane) and 0.5mol% of triphenylsulfonium triphlate for molecular weight 281 expressed in terms of monomer unit thereof thus forming a resin layer 15. It is then heated and irradiated with UV-ray to form a tin oxide glass layer 16 followed by formation of an SAL 601 layer 17. Thereafter, a resist pattern 18 is formed by electron beam photolithography and the tin oxide glass layer 16 is etched to form an intermediate layer pattern 19. Finally, a lower layer pattern 14 is formed using the resist pattern 18 and the intermediate layer pattern 19 as a mask followed by formation of a gate electrode 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique used in manufacturing semiconductor devices and the like, and more particularly to a pattern forming method for realizing highly accurate electron beam lithography.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, some documents were described in the following documents. Literature; Proceedings of the 40th Joint Lecture on Applied Physics,
1993, Keiko Yano et al., "Antistatic Agent Using Alkali-Soluble Conductive Polymer-Application to Chemically Amplified Resist," P. 555 In recent years, the resolution of optical lithography is becoming incompatible with the high integration of LSIs, and expectations for electron beam lithography are increasing. As is well known, LSI
With higher integration and higher speed, patterns having a high aspect ratio have been formed on a substrate to be processed.
For this reason, the film thickness of the resist layer tends to be flattened, and the resist layer tends to be thick enough to be maintained as a mask until the end of processing. Therefore, the resolution of the resist is lowered, and it is becoming difficult to process the substrate as desired with a single resist layer. In order to avoid this problem, electron beam lithography uses a method in which the resist is a three-layer resist, if necessary.

FIG. 2 is a diagram showing a conventional three-layer resist layer. As shown in FIG. 2, the three-layer resist layer is a lower layer 3 formed of a thick polymer layer for planarizing the substrate step 2 on the substrate 1, and a thin silicon oxide film layer as an etching mask for the lower layer 3. The intermediate layer 4 is formed, and the upper layer resist 5 is formed of an electron beam resist layer as an etching mask for the intermediate layer 4. First, the upper layer resist 5 is patterned by exposing and developing with an electron beam, and the intermediate layer 4 is patterned using the patterned upper layer resist 5 as a mask. Then, the lower layer 3 is patterned using the upper resist 5 and the intermediate layer 4 as a mask, and the substrate 1 to be processed is further patterned. But,
In such a thick insulating layer having a three-layered resist structure, in drawing using an electron beam which is a charged particle, the insulating layer is charged up by the irradiation of the electron beam. The electron beam is bent by the Coulomb force due to the charged-up electrons, causing a displacement. Therefore, deterioration of drawing accuracy becomes a problem. Therefore, it is general to add an antistatic layer. FIG. 3 is a diagram showing a conventional four-layer resist layer including the antistatic layer described in the above document. FIG.
As described above, by applying and forming the water-soluble chargeable polymer layer 6 on the upper layer resist 5 in FIG. 2, it is possible to perform highly accurate electron beam drawing.

[0004]

However, the conventional pattern forming method has the following problems (a) to (a).
There was (c). (A) In order to form the conductive polymer layer 6 on the upper layer,
There is a problem that the resolution is deteriorated due to the proximity effect due to the scattering of electrons (forward scattering) in the conductive polymer layer 6 when the electron beam is irradiated. (B) Depending on the type of the upper layer resist 5, mixing of the upper layer resist 6 may occur when the conductive polymer layer 6 is applied, the development characteristics may change, and a problem may occur during development. (C) Depending on the type of the upper layer resist 5, there is a problem that a step of peeling off the conductive polymer layer 6 is required after the drawing and before the development of the upper layer resist 5, resulting in an increase in the number of steps.

[0005]

In order to solve the above-mentioned problems, the pattern forming method of the first invention comprises a step of forming an underlayer film on a substrate for processing, and a resin layer applied to the underlayer film. A step of forming (for example, polystannoxane) and a step of curing the resin layer to form a tin oxide glass layer are performed. Then, a step of forming an upper layer resist film, a step of patterning the upper layer resist film by electron beam lithography to form a resist pattern, and a step of patterning the tin oxide glass layer using the resist pattern as a mask to form an intermediate layer. A step of forming a layer pattern, patterning the lower layer resist using the resist pattern and the intermediate layer pattern as a mask,
And a step of forming a lower layer resist pattern.

[0006]

According to the first aspect of the invention, since the pattern forming method is configured as described above, after the resin layer is formed on the lower layer film, the resin layer is cured to form the tin oxide glass layer. Next, an upper layer resist film is formed and the upper layer resist is irradiated with an electron beam. Since the tin oxide glass layer has conductivity, it is prevented from being charged by the electron beam irradiation. As a result, displacement due to charge-up is prevented.
Further, since nothing is formed on the upper resist film, electrons are not scattered, so that the resolution due to the proximity effect does not deteriorate. Therefore, the above problem can be solved.

[0007]

EXAMPLE FIGS. 1A to 1H are process diagrams showing a pattern forming method according to an example of the present invention. The point that the pattern forming method of the embodiment of the present invention is different from the conventional pattern forming method is that the intermediate layer in the three-layer resist has tin oxide-based glass (having a composition mainly consisting of tin oxide,
Hydrogen (H) is included). Below, Figure 1
The pattern forming method of the embodiment of the present invention will be described with reference to (a) to (h). (1) Step of FIG. 1A After forming a field oxide film (not shown) on the silicon substrate 11 by an element isolation method, a gate oxide film 12 is formed by a thermal oxidation method. CV is formed on the gate oxide film 12.
A polysilicon film 13 is formed by the D method, and a processing substrate is prepared. After that, a film thickness of 1.
A microposit photo resist 14 (manufactured by Shipley Co.) is formed as a lower layer film which is made of a 5 .mu.m hot coin. (2) Process of FIG. 1 (b) Poly (di-t-butoxystannoxane: (—Sn—O—) _n having a molecular weight of 2400 and a molecular weight dispersion of 1.2 and two OC _{4 s)}
H ₉ ) and 0.5 mol% of triphenylsulfonium triflate (monobenzene ring and S ⁺ CF ₃ SO ₃ ) based on its molecular weight 281 in terms of monomer units.
A cyclohexanone solution containing (bonding with) is spin-coated to form a resin layer 15 having a film thickness of 0.3 μm.

(3) Step of FIG. 1 (c) The resin layer 1 is irradiated with ultraviolet rays while being heated to 150 ° C.
The tin oxide glass layer 16 is formed by curing 5 (UV curing). The chemical reaction of the tin oxide glass layer 16 changes the butoxystannoxane into the tin oxide glass layer 16 by heating with triphenylsulfonium triflate as a catalyst. (4) Step of FIG. 1D As the upper resist film, SAL601 having a film thickness of 0.4 μm is used.
A layer (made by Shipley) 17 is formed. At this time, the SAL601 layer 17 is not formed in the peripheral portion of the silicon substrate 11 and the tin oxide glass layer 16 is exposed. (5) Step of FIG. 1 (e) Using an electron beam with an acceleration voltage of 20 kV, the exposure dose is 10 μC /
Draw a high density pattern in cm ² . The electron beam irradiation is
With the position of the electron gun and the silicon substrate 11 fixed, the SAL 601 having a constant width is deflected by deflecting the electrons.
The area of layer 17 is illuminated. Then, after irradiating a region having a constant width, the silicon substrate 11 is scanned in a constant direction,
Further, electron beam irradiation is performed. For this reason, in the long and narrow areas such as the wirings, the joints formed by the scanning of the silicon substrate 11 can be formed as the connecting portions. Further, the tin oxide glass layer 16 exposed at the peripheral portion of the silicon substrate 11 is fixed by applying a metal claw which is a supporting portion of the silicon substrate 11 of the electron beam exposure apparatus. Thereby, the electron beam reaches the tin oxide glass layer 16 by the acceleration voltage, and the tin oxide glass layer 1 which is a conductor is
6. Escape through the metal claw that is at ground potential, preventing charge-up. However, tin oxide glass layer 1
Even if 6 is not in contact with the metal nail, electrons diffuse to some extent in the tin oxide glass layer 16 which is a conductor. Then, after baking at 115 ° C. for 2 minutes, it is developed with a dedicated developing solution and rinsed with pure water to form a resist pattern 18.

(6) Step of FIG. 1 (f) Using the resist pattern 18 as a mask, CF ₃ / O ₂ = 48/2 sccm as an etching gas and a gas pressure of 1.
The tin oxide glass layer 16 is etched under the conditions of 5 Pa and a power density of 0.12 W / cm ² to form an intermediate layer pattern 19. (7) Step of FIG. 1G Using the resist pattern 18 and the intermediate layer pattern 19 as a mask, the lower layer 14 is etched under conditions of an etching gas O _{2 of} 50 sccm, a gas pressure of 1.0 Pa, and a power density of 0.12 W / cm ^2. Thus, the lower layer pattern 14 is formed. When this pattern was observed with a scanning electron microscope (SEM), it was confirmed that a line and space width of 0.3 μm (hereinafter referred to as L / S (Line and Space)) was resolved. (8) Step of FIG. 1H The polysinccon film 14 is etched using the resist pattern 18, the intermediate layer pattern 19 and the lower layer pattern 20 as a mask to form a high density gate electrode 21. Then, the resist pattern 18, the intermediate layer pattern 19 and the lower layer pattern 20 are removed. Then, the gate electrode 21 having a width of 0.3 μm is formed.

As described above, this embodiment has the following advantages. When the upper layer pattern after electron beam drawing was observed with a length-measuring SEM, the gate electrode 21 was observed in the 0.5 μmL / S region.
The amount of connection shift at the joint due to the scanning of the silicon substrate 11 during the irradiation of the electron beam of the pattern was 0.02 μm.
On the other hand, when the silicon oxide film was used as the intermediate layer in the same process, the pattern of the gate electrode was not connected and the deviation amount was 1.1 μm. This is caused by the problem of resolution deterioration due to forward scattering of electrons by placing a conductive polymer layer on the upper layer of the prior art and charge-up at the time of drawing by placing a silicon oxide film as an insulator in the intermediate layer. This is because the problem of misalignment of the drawing position was solved by the adoption of the tin oxide film. Further, since the organic solvent is insoluble in the tin oxide film, mixing did not occur at the time of coating the upper layer, and the developing characteristics did not change. Furthermore, since the intermediate layer of the conventionally used three-layer resist is only replaced with tin oxide, the number of steps does not increase. Further, this intermediate layer can be formed by a simple method such as spin coating and UV curing, and the process from the lower layer 14 to the formation of the resist 17 of the upper layer can be performed in the same chamber, which is simple. In addition,
The present invention is not limited to the above embodiment, and various modifications can be made. The following are examples of such modifications. In this embodiment, the method of forming the pattern of the gate electrode has been described, but it can be used not only for the electrode or wiring pattern like the gate electrode, but also for opening contact holes.

[0011]

As described in detail above, according to the first and second inventions, the conductive tin oxide glass layer is used as the intermediate layer, so that charge-up and electron scattering due to electron beam lithography are prevented. It is possible to form an accurate and high-density pattern.

[Brief description of drawings]

FIG. 1 is a process chart showing a pattern forming method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional three-layer resist layer.

FIG. 3 is a diagram showing a conventional four-layer resist layer.

[Explanation of symbols]

 11 Silicon Substrate 12 Gate Oxide Film 13 Polycincon Film 14 Lower Layer 15 Resin Layer 16 Tin Oxide Glass Layer 17 Resist 18 Resist Pattern 19 Intermediate Layer Pattern 20 Lower Layer Pattern 21 Gate Electrode

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/312 D H01L 21/30 561

Claims (2)

[Claims] 1. A step of forming an underlayer film on a processing substrate, a step of applying on the underlayer film to form a resin layer, and a step of curing the resin layer to form a tin oxide glass layer. A step of forming an upper layer resist film on the tin oxide glass layer, a step of patterning the upper layer resist film by electron beam lithography to form a resist pattern, and the tin oxide glass layer using the resist pattern as a mask. And forming an intermediate layer pattern, and using the resist pattern and the intermediate layer pattern as a mask, patterning the lower layer resist to form a lower layer resist pattern. Pattern formation method. 2. The pattern forming method according to claim 1, wherein the resin layer contains polystannoxane.