JPS63266830A - Flattening method for surface - Google Patents

Abstract

PURPOSE:To obtain a preferably flat surface over a whole wafer even when the wafer has a large bore diameter by depositing a silicon film on an SiO2 formed with an uneven part on its surface in thickness of the stepwise difference of the uneven part on the SiO2, selectively polishing the silicon film, and etching the SiO2 and the silicon at an equal velocity. CONSTITUTION:A device layer 2 is formed on a silicon substrate 1, and an SiO2 3 which becomes a device protecting and interlayer insulating film is formed thereon. Since the surface of the device layer becomes an uneven shape, the upper surface of the SiO2 3 becomes uneven shape by reflecting it. A silicon film 4 is formed by an LPCVD method on the SiO2 3. When the film 4 is selectively polished, the bumps of the SiO2 3 become stoppers, thereby automatically stopping the polishing, the silicon film remains on the recesses of the SiO2 so that the surface becomes flat. This selective polishing is conducted by securing the wafer to a supporting plate with wax, with polyester polishing pad and ethylenediamine.pyrocatechol aqueous solution. Then, dry etching for equalizing the etching velocity for the silicon and the SiO2 is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for planarizing the surface of SiO2 in the manufacturing process of semiconductor devices.

[Prior Art] In the manufacturing process of semiconductor devices and integrated circuits, irregularities are inevitably created on the surface of the device layer due to the process of forming individual transistors, wiring, etc. that constitute these devices. This unevenness further becomes a major hindrance to subsequent processes such as multilayer wiring. Further, even in the production of a so-called three-dimensional circuit element having a structure in which active layers are laminated in multiple layers with insulating layers such as SiO2 interposed therebetween, the presence of irregularities on the surface of this SiO2 is inconvenient for forming the active layer thereon.

Conventional surface planarization methods include spin coating a fluid organic film followed by constant speed dry etching, and polishing.

[Problems to be Solved by the Invention] However, in the method using spin coating and constant speed dry etching, flattening of the fluid organic film in the first step is a problem. In other words, because the fluidity is not necessarily sufficient, unevenness remains on the surface, or shrinkage of the film always occurs during the baking heat treatment before dry etching.
Since the film is thicker in the recessed portions than in the convex portions, the amount of shrinkage is greater, and as a result, the remaining unevenness is enlarged.

On the other hand, in the polishing method, the flatness seen locally is extremely good, but there are problems with uniformity over the entire large diameter surface due to warpage of the wafer, uneven thickness, etc.

The present invention has been made in order to solve the above-mentioned conventional problems, and provides a surface flattening method that can obtain a good flat surface over the entire wafer even for large diameter wafers. The purpose is to

[Means for Solving the Problems] The present invention provides S! a silicon film on SiO2 with an uneven surface. A step of depositing the silicon film to a thickness equal to or greater than the level difference between the concavities and convexities on the 510
forming a flat surface using the convex portion of No. 2 as a stopper;
By performing the uniform etching of SiO2 and silicon,
This is a surface flattening method characterized by comprising a step of forming an O2 flat surface.

[Function] An important point in the present invention is that silicon is used to fill the recesses in SiO2 in the first step of planarization (the step of filling the recesses on SiO2 and flattening it), and that following this planarization step, silicon is used to fill the recesses in SiO2. The method is to use selective polishing of silicon using SiO2 as a stopper. Selective polishing is a method that utilizes a chemical reaction between silicon and a polishing solution followed by mechanical removal of the reaction product. For silicon, the polishing speed is, for example, 10 m/h, but for SiO2, On the other hand, there is a method of using a substance that does not cause the above-mentioned chemical reaction, so that the polishing rate becomes substantially zero. As a result, the flatness and uniformity within the large-diameter wafer at the stage of selective polishing are extremely good, and the subsequent uniform etching of silicon and SiO2 achieves final planarization of the 8102 surface.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a process diagram showing an embodiment of the method of the present invention.

FIG. 1(a) shows a state in which a device layer 2 is formed on a silicon substrate 1, and SiO 23 serving as a device protection and interlayer insulating film is formed thereon. Since the surface of the device layer has an uneven shape, the upper surface of the SiO 23 also has an uneven shape reflecting this.

Figure 1(b) shows a silicon film 4 formed on SiO23 by LPCVD.
The upper surface of the silicon film 4 is shown to be formed by the method, and the upper surface of the silicon film 4 is uneven. FIG. 1(C) shows that by selectively polishing the silicon film 4, the convex portion of the SiO23 acts as a stopper and the polishing is automatically stopped.
This shows a state in which the silicon film remains in the recessed portion of No. 2 and the surface is flat. In this example, the selective polishing was performed by fixing the wafer to a support plate with wax and using a polyester polishing pad and an aqueous solution of ethylenediamine/pyrocatechol. At this time, no abrasive material was used. Next, by performing dry etching to equalize the etching speed for silicon and SiO2,
Planarization of SiO2 as shown in FIG. 1(d) is completed.

Note that in the state shown in Figure 1(a), the level difference in the unevenness of SiO23 was 1.5 degrees, but the final level difference in the unevenness of SiO23 was 5008 degrees, and it was well uniform over the entire surface of the 4-inch wafer. I got sex.

[Effect of the invention] As explained above, according to the method of the present invention, SiO2
In surface planarization, the first step of flattening the surface by filling silicon into the recesses of SiO2 is extremely complete. Further, since this process has an automatic polishing stop mechanism by selective polishing using the convex portion of SiO2 as a stopper, the uniformity within the large diameter wafer is also good. As a result, uniform SiO is formed over the entire wafer surface.
2 flat surfaces can be obtained.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an embodiment of the method of the present invention.

Claims (1)

[Claims] (1) A step of depositing a silicon film on the SiO_2 whose surface is uneven, to a thickness equal to or greater than the level difference of the unevenness on the SiO_2, and selectively polishing the silicon film,
A surface flattening method characterized by comprising a step of forming a flat surface using the convex portion of _2 as a stopper, and a step of etching the SiO_2 and silicon at a constant rate to form a flat surface of SiO_2. .