JP2853626B2 - Substrate surface flattening method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a very smooth surface by eliminating minute steps on a substrate.

[0002]

2. Description of the Related Art For example, in the process of manufacturing a semiconductor device, when a step is formed on a substrate, inconveniences such as disconnection of a wiring formed thereon and deterioration of photolithography processing accuracy occur. Performing flattening to eliminate it is widely practiced as part of the process today (for example, Susumu Namba, “Submicron Lithography Comprehensive Technical Documents,” 1985 Science Forum, p. 312, Tadakawa Tadahiro et al. “Innovation in ULSI lithography technology”, Science Forum, p. 71, 1994).

[0003] Among various flattening techniques, a coating flattening technique, that is, an SOG (spin-on-glass) method or a coating method of a polymer solution is simple and frequently used. FIG. 2 is a sectional view showing a conventional flattening method. Substrate 1 with steps
A polymer solution such as a photoresist is spin-coated on 1 and baked to form a polymer spin-coated film 12.
According to this method, the recess can be buried with the polymer film to reduce the step.

A method of forming an SOG film or a polymer film to planarize the surface, and then performing etchback or CMP (chemical mechanical polishing) to remove all or part of the SOG film or the polymer film is also available. Often used. In addition, when an SOI (Silicon on Insulator) substrate is manufactured by a bonding method, it is required to finish the surface of the substrate extremely flat. Conventionally, however, it is general to flatten the surface using a CMP method or the like. Was.

[0005]

The above-mentioned planarization methods using a coating film are routinely used as semiconductor manufacturing techniques, but they cannot completely eliminate minute steps. This is because in SOG, grains of a considerable size grow during the baking process, and the polymer itself has a surface roughness of nanometer (nm) size or more (Toshiyuki Yoshimura et al. Size Effect of Resist Polymer in Meter Lithography ”Applied Physics November 1994 Issue 11
31 pages, Japan Society of Applied Physics). Even if etch back or CMP is performed after the formation of the flattening film, if the flatness of the surface of the initially formed SOG film or polymer film is not good, the flatness is not significantly improved by subsequent processing. That is, in the prior art, although a step difference of not less than a micrometer (μm) can be approximately eliminated, flattening in a nanometer region is insufficient or impossible.

[0006]

[Means for Solving the Problems] One micrometer (μ
m) If a spin coating film of calixarene is formed on a substrate having the following minute steps, the steps can be eliminated by this coating film to obtain an extremely flat surface.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of flattening a substrate surface according to the present invention, as shown in FIG. 1, a calixarene or a calixarene derivative solution is spin-coated on a substrate 1 having minute steps, scratches and roughness. The calix arene spin coat film 2 is formed on the substrate surface by performing baking, whereby the steps and the like are eliminated to obtain an extremely flat surface state.

[0008] Calixarenes are cyclic oligomers formed by the condensation of phenol-formaldehyde. The present applicant has already developed a calixarene derivative which is soluble in an organic solvent, and has shown that a good film can be obtained by spin-coating the calixarene derivative (Japanese Patent Laid-Open No. 4-12).
No. 8253), we have reported that a calixarene film spin-coated on a substrate has a surface roughness of 1 to 2 nm.
That it forms an extremely smooth surface,
This has been used to make an invention for use in flattening the substrate surface.

Such smoothness cannot be expected at all from a coating film formed by spin-coating a polymer.
This is considered to be due to the fact that calixarene molecules (degree of polymerization: about 4 to 8) are very roughly cluster-like molecules having a diameter of 1 nm. That is, when this solution is applied using a spinner, the calixarene molecules roll on the surface to fill the concave portions, so that the step of the film is considered to be within one or two molecules. When baking is performed in this state to evaporate the solvent, a firm film having a step of about 1 to 2 nm can be formed. Based on this finding, the present invention forms a spin coating film of calixarene or a derivative thereof on a substrate having minute steps and scratches, roughness, and the like, thereby eliminating steps and thereby obtaining an extremely flat surface. It is like that.

[0010]

Next, a preferred embodiment of the present invention will be described. [Example 1] Methyl calix [6] arene acetylated product (5, 11, 17, 23, 29, 35-hexamethyl, 37, 38, 39, 40, 41, 42- hexaacetoxy calix [6] arene) ( A 3% by weight monochlorobenzene solution (see Japanese Patent Publication No. Hei. 23-23340) is prepared, spin-coated on a clean silicon wafer substrate, and dried in a nitrogen atmosphere.
Baking was performed at 0 ° C. for 30 minutes to obtain a firm film having a thickness of about 150 nm.

The surface roughness was measured using an AFM (atomic force microscope) to find that it was 1 to 2 nm, at most 3 n
Only irregularities of about m were observed. This smoothness is observed when spin-coating polymers such as resist,
It has a very high degree of smoothness as compared with a roughness of 10 nm or more. As described above, this calixarene molecule can be considered very roughly as a cluster having a diameter of about 1 nm, and this shape is considered to contribute to the formation of an extremely smooth surface. FIG. 2 shows a photograph of the surface roughness measured by AFM.

Example 2 The same calixarene solution as in Example 1 was spin-coated on a substrate having a shallow scratch of 1 μm or less on the surface to obtain a calixarene spin-coated film. When the surface irregularities were measured using AFM, the same results as in Example 1 were obtained, and it was found that the irregularities on the substrate surface were eliminated.

Reference Example 1 When the same spin coating as in Example 1 was applied to a substrate having a step of 3 μm on the surface, the calixarene film was cut off and could not be flattened.

Example 3 The same calixarene solution as in Example 1 was spin-coated on a silicon wafer substrate having a step of 1 μm or less on the surface to obtain a calixarene spin-coated film. Next, the calixarene was removed by etch-back by reactive ion etching (RIE) using CF ₄ . When the unevenness of the silicon wafer surface was measured using AFM, it was found that only an unevenness of 5 nm or less was observed, indicating that an extremely flat surface was obtained.

Reference Example 2 A mirror-finished silicon wafer substrate having a maximum step of 50 nm was etched back by RIE without forming a calixarene coating film, but the step could not be eliminated.

[0016]

As described above, the flattening method according to the present invention forms a calixarene spin coating film on a substrate having a minute step, so that a fine step can be formed by a simple method. Thus, a substrate having an extremely smooth surface which cannot be achieved by the conventional method can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention.

FIG. 2 is an atomic force microscope (AFM) photograph showing the surface morphology of the calixarene film.

FIG. 3 is a cross-sectional view illustrating a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Substrate 2 Calixarene spin coat film 12 Polymer spin coat film

Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI H01L 21/3065 H01L 21/302 L (56) References JP-A-6-275508 (JP, A) JP-A-4-336433 (JP, A JP-A-6-228032 (JP, A) JP-A-6-196440 (JP, A) JP-A-4-15232 (JP, A) JP-A-59-72725 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B05D 1/40 B05D 3/00-3/12 B05D 7/24 302 H01L 21/302

Claims (1)

(57) [Claims] 1. A calixarene or calixarene derivative solution is spin- coated on a substrate having minute steps of 1 micrometer (μm) or less, and baked to obtain a coating film of calixarene or a derivative thereof.
Etchback or CMP at least a portion of the coating
(Chemical mechanical polishing).