JPS6266635A - Flattening method - Google Patents

Abstract

PURPOSE:To obtain a flat insulating film on a step by coating it with resin which mainly contains siloxane polymer to flatten a certain surface of the step, oxidizing the upper layer to modify it to an SiO2 film, selectively removing it and then oxidizing the remaining resin film as SiO2 film. CONSTITUTION:A substrate 1 having a step of approx. 0.5mum is rotatably coated with siloxane polymer to form a resin film 5 of approx. 1mum thick, and the film is treated at 200 deg.C in N2. When using a polymer having CH3 group and OH group as substituted groups and a 3-dimensional structure, the polymer can be coated in large thickness, and a crack hardly occurs at contraction time. An upper layer film 6 is converted to SiO2 to 0.3mum thick of the film 5 from the projection of the substrate 1. Only the film 6 is selectively removed with aqueous HF solution, the remaining film 5 is completely converted to SiO2 by plasma oxidizing to modify it to an insulating film 6. This flattening method has less crack, simple steps, and ready process controllability to be utilized for various processes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for planarizing the surface of a semiconductor substrate having a step on the surface in a semiconductor device manufacturing process.

[Conventional technology]

Conventionally, in the manufacturing process of large-scale integrated circuits (LSI),
To planarize the surface of the interlayer insulating film of multilayer wiring or the interlayer insulating film of a stacked semiconductor device, various methods such as phosphor glass flow, resin insulation method, resin coating, and etching are used. For example, in Document 1 Flattening Technology # by Kaion Takahama published in the 1st Next Generation Industrial Basic Technology Synd, July 1988, pages 192 to 195,
A method of flattening spin-on glass by coating and etching the entire circumference has been reported.

The spin-on used in this planarization method is a solution mainly composed of last-hasilanol (81(OH)4), which is spun onto a semiconductor substrate and then solidified by heat treatment to form a SlO It is something that forms. The basic steps of this planarization method will be explained below with reference to the schematic cross-sectional views shown in FIGS. 2(a) and 2(b) (C).

In the figure, 1 is the base substrate, 2 it CVD 810211
In 3, the spin-on is a lath film immediately after coating, and in 4, 5tO
This is a divisible spin-on glass film. First, Figure 2 (,
), an SIO□ film 2'1 corresponding to the glabellar insulating film is formed on the base substrate 1 having a step by the CVD method,
Next, spin-on glass was applied using a spin coating method to fill in the steps to flatten the surface.Next, as shown in Figure 2(b), heat treatment was performed at 800°C for 1 hour in a nitrogen atmosphere. Yosis pin-on solidifies the lath coating film 3 and 810□
The coating film 4 is changed in quality. At this time, the thickness of the coating film 4 decreases due to the condensation reaction of the spin-on glass coating film 3. Finally, as shown in FIG. JIB is etched at the same etching speed to the required thickness.

[Problem that the invention seeks to solve]

The flattening method described above is possible because spin-on glass is a liquid material that can flatten the surface by spin coating, and because it is converted to 810□ by heat treatment, there is no adverse effect due to impurity contamination, and it is not converted into StO. It has the advantage that it is possible to leave the coated film 4 made of spin-on glass as it is. However, on the other hand, the reaction of forming the StO□ coating film on glass is basically based on the condensation reaction of silanol monomers as described below, and has the disadvantage of a high volume shrinkage rate and a tendency to generate cracks.

In addition, as mentioned above, since the spin-on glass film is mainly composed of silanol monomer, it is difficult to apply it thickly.For example, K, which flattens a level difference of approximately 1μ, is coated 4 to 5 times. There is a need.

Furthermore, the StO□ silanol coating film and the base CV
It is very difficult to controllably etch D8102 films to the required thickness at uniform etch rates. As described above, the above-mentioned planarization method has problems with reliability such as the occurrence of cracks, and requires a large number of steps and is difficult to control, so it is considered difficult to use as a method for preparing LSIs. Ta.

An object of the present invention is to provide a planarization method that solves the above problems.

[Means for solving problems]

The present invention flattens the surface of a semiconductor substrate having steps.
In this method, the surface is flattened by coating the substrate with a resin containing siloxane-based I□1 reamer as a main component, and then the upper layer of the resin film is oxidized to change the quality of the StO□ button. This method forms a flat insulating film on the step formed on the semiconductor substrate by selectively etching away only the upper layer that has been converted to 5tO2 and oxidizing the remaining resin film to change its quality to 810□. be.

An important point of the planarization method of the present invention is that a resin containing a siloxane-based polymer as a main component is used as a coating material for planarizing the surface of a semiconductor substrate having steps, and this resin does not oxidize. This takes advantage of the fact that the image is converted into 810□.

Here, the conversion of the resin into StO□ by oxidation may be performed by heat treatment in an oxygen atmosphere, oxygen plasma oxidation, or heat treatment in an ozone atmosphere.

[Effect]

Siloxane-based/IJ mom-Basically, it forms a two-dimensional polymer as shown in (A) below or a three-dimensional polymer as shown in (B).

RR (A) (B) Here, R corresponds to a substituent such as H, OH, CM, #C2H5, or a phenyl group. Such polymer structures can be coated thickly with monomers such as silanols. Furthermore, the shrinkage rate due to heat treatment after coating can be reduced by selecting substituents.

Moreover, such a siloxane-based polymer is oxidized to StO by heat treatment in an oxygen atmosphere, oxygen plasma oxidation, or heat treatment in an ozone atmosphere. At this time, since the oxidation reaction proceeds from the upper layer of the siloxane polymer film, it is possible to control the thickness of the 5tO2 film by adjusting the oxidation conditions. Furthermore, siloxane-based polymers are hardly etched by hydrofluoric acid-based solutions, whereas 810□
The etching rate of the siloxane-based polymer is high. Therefore, only the upper layer of the applied siloxane-based polymer film is S
It is possible to selectively remove only the siloxane-based 74 remer film that has been converted into iO2 and converted into StO□ with a 7-acid-based etching solution, and finally the remaining siloxane-based polymer film can be completely converted into StO□. .

〔Example〕

Hereinafter, an embodiment of the planarization method according to the present invention will be described based on the schematic cross-sectional views of FIGS. 1-(b)-(c) and (d).

In the figure, 1 is the same base substrate as 1 in Figure 2, 5 is a resin film mainly composed of siloxane polymer, and 6 is SiO2.
This is a resin film whose main component is a siloxane-based polymer. First, as shown in FIG. 1 (1), a resin film 5 was formed by applying a 91.0 μm thick siloxane-based polymer on a base substrate l having a step of 0.5 μm on the surface by a spin coating method. Heat treatment was performed at 200° C. for 1 hour in a nitrogen atmosphere. Here, as the siloxane polymer, a streamer having a substituent K CM group and an OH group and having a three-dimensional structure was used. This siloxane-based polymer can be applied thickly at one time, and has a small shrinkage rate during the condensation reaction, so cracks are less likely to occur. Next, Figure 1 (b
), the upper resin film 6't-oxidized to StO Resin 1 [changed to 6]. The plasma oxidation conditions at this time are:
Using a cylindrical concealed glazma generator, 0□ has a gas flow rate of 20 s.
ecm, W pressure 1.2 Torr s High frequency power 20
At 0th order which is 0W, K as shown in Fig. 1(e) Ilc,
7-acid aqueous solution (IF: H2O-1: 30) Il
Only the 5io2 resin film 6 in the upper layer part c was selectively removed by etching. Finally, as shown in FIG. 1(d)k, the remaining resin film 5 is completely oxidized under the plasma oxidation conditions.
810□ and changes into resin [6]. In this way, we were able to form a flattened insulating film, ie, a resin film 6 made of StO2, on the step to a thickness K of 0.3 μm.

As described above, according to the above embodiment, spin-on has the same effect as the conventional planarization method using a lath, can be applied thickly at one time, reduces the occurrence of cracks, and can control the thickness of the planarized insulating film. A planarization method has been obtained that solves the problems of conventional planarization methods, such as easy flattening.

In this example, a resin whose main component is a siloxane-based polymer having a three-dimensional structure with CH, and OH groups as substituents was used as the resin to be applied, but other resins whose main component is a siloxane-based polymer may be used. But it is possible. In addition, the resin St
Oxygen plasma oxidation was used as the method for O□ conversion, but other heat treatment in an oxygen atmosphere or heat treatment in an ozone atmosphere may also be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a planarization method that is significantly improved compared to conventional planarization methods, such as less occurrence of cracks, a simpler process, and easier process control.

Therefore, the present inventors can provide a planarization method that is highly reliable and has a relatively short TAT, and has the effect that it can be widely used in various processes that require planarization in the LSI assembly process.

[Brief explanation of drawings]

FIGS. 1(aMb), (e), and (d) are schematic cross-sectional views showing an example of the manufacturing process of the flattening method according to the present invention 1511, and FIGS. 2(a), (b), and (e ) is a schematic cross-sectional view showing the manufacturing process of a conventional planarization method. l... base substrate, 5... siloxane-based remer t-
Resin film mainly composed of 6...Resin film mainly composed of siloxane polymer converted into StO□. Patent applicant NEC Corporation - <b> Figure 1 (α) Cb) 2--CVD5LOzFI Figure 2

Claims (1)

[Claims] (1) In a method for flattening the surface of a semiconductor substrate having a step, the surface is flattened by applying a resin containing a siloxane-based polymer as a main component onto the step of the substrate,
Next, the upper layer of the resin film is oxidized to transform into SiO_2, and only the upper layer that has been converted to SiO_2 is selectively etched away, and the remaining resin film is oxidized and transformed to SiO_2 to form on the semiconductor substrate. A planarization method characterized by forming a flat insulating film on the stepped step.