JPH0281429A - Method of etching polycrystalline silicon - Google Patents

Abstract

PURPOSE:To avoid water marks and eliminate the unetched remnants of a polycrystalline silicon film by a method wherein the surface of the polycrystalline silicon film is treated with solution containing hydrogen peroxide to form a hydrophilic surface and then etching is carried out. CONSTITUTION:A polycrystalline silicon film 2 is built up on the surface of an insulating film 1 made of SiO2. The surface of the polycrystalline silicon film 2 is subjected to light etching with fluoric acid, washed with flowing water and treated with solution of hydrochloric acid and hydrogen peroxide. Particles and the like existing on the surface of the polycrystalline silicon film 2 and the insulating film 1 are washed and removed by the action of HCl. Further, the thin portion of the surface of the polycrystalline silicon film 2 is oxidized by the oxidation action of H2O2 and converted into an SiO2 film 5 having a uniform thickness and its surface becomes hydrophilic. The etching can be made to progress uniformly and the unetched remnants of the polycrystalline silicon film are eliminated from the surface of the insulating film 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of etching polycrystalline silicon, particularly dry etching.

[Summary of the Invention] The present invention provides a method for etching polycrystalline silicon, in which the surface of a polycrystalline silicon film is treated with a solution containing hydrogen peroxide to make the surface hydrophilic, and then etching is performed. It is possible to easily make the surface of polycrystalline silicon hydrophilic without having to pay attention to water washing time or wafer pulling speed, thereby preventing the formation of water marks caused by water droplets and suppressing the etching residue of polycrystalline silicon. This is what I did.

[Prior Art] Conventionally, when dry etching polycrystalline silicon used for gate electrodes of semiconductor devices, high resistance elements, etc., the surface of polycrystalline silicon is subjected to light etching with diluted hydrofluoric acid, washing with running water, etc. as a pretreatment. is being carried out.

[Problem to be solved by the invention] However, in such conventional methods, water droplets (water marks) are generated on the surface of polycrystalline silicon due to light etching with hydrofluoric acid and washing with running water as pre-treatment. There's a problem.

That is, for example, as shown in FIG. 4A, Sig! When etching the polycrystalline silicon film 2 laminated and formed on the insulating film l, the hydrophobic surface of the polycrystalline silicon film 2 is etched by light etching on the surface of the polycrystalline silicon pattern 2 or washing with running water. Water droplets 3 adhere. Oxygen in the atmosphere is dissolved in the water droplets 3, and this oxygen oxidizes silicon to form a watermark 4 made of SiOx on the surface of the film 2 (see Section 3).

Figure 4B). When dry etching is performed in such a state, the watermark 4 becomes an etching mask,
As shown in FIG. 4C, etching residues 2a of polycrystalline silicon are formed on the insulating film I, which causes defects in the manufacturing process.

In order to solve the problems caused by watermarks, it is possible to slow down the rate at which water is drawn from the water tank so that no water droplets remain on the polycrystalline silicon surface, or to make the water run extremely long so that no water droplets remain on the polycrystalline silicon surface. It has been considered to make the material hydrophilic so that water droplets do not remain on the surface, but both methods have problems such as being time consuming and having poor controllability.

The present invention was devised in view of these conventional problems, and provides an etching method that can easily change the surface of polycrystalline silicon to be hydrophilic and leaves no etching residue. .

[Means for Solving the Problems] Therefore, the present invention comprises treating the surface of a polycrystalline silicon film with a solution containing hydrogen peroxide to make the surface hydrophilic,
Next, the solution is to perform etching.

[Function] The surface of the polycrystalline silicon film is uniformly oxidized by being treated with a solution containing hydrogen peroxide and becomes hydrophilic.
Water droplets (water beads) do not adhere, and an etching mask made of SiOx is not formed.

Therefore, the polycrystalline silicon film is etched uniformly, and no etching residue is left.

[Example 7] Details of the polycrystalline silicon etching method according to the present invention will be explained below based on an example shown in the drawings.

FIG. 1 is a process diagram showing an embodiment of the polycrystalline silicon etching method according to the present invention, and FIGS. 2A to 2C are cross-sectional views thereof.

In the figure, 1 is an insulating film made of Sin, and a polycrystalline silicon film 2 is deposited on the surface by CVD method (second
(Figure A) First, in such a structure, the surface of the polycrystalline silicon film 2 is subjected to light etching using hydrofluoric acid, and then,
Rinse with running water.

Then hydrochloric acid (MCI2) and hydrogen peroxide (H! O!
) and water (H, O) is MCI2: H, O,: H
, O=1:I:8 solution for about 10 minutes.

At this time, particles and the like existing on the surfaces of the polycrystalline silicon film 2a and the insulating film 1 are cleaned and removed by the action of the MCI 2. Further, the surface of the polycrystalline silicon film 2 is
Due to the oxidizing action of 2O, the SiOx film 5 is thinly oxidized and has a uniform thickness, and its surface becomes a hydrophilic surface (FIG. 2B).

Next, after washing with running water, a drying process is performed.

After drying, EC is applied as dry etching.
Perform R plasma etching to remove polycrystalline silicon film 2.
is removed to expose the insulating film 1 (FIG. 2C). At this time, since the Si○ film 5 is formed with a uniform thickness on the surface of the polycrystalline silicon film 2, the etching should proceed evenly. There is no.

Although the embodiment has been described above, various other design changes are possible.For example, in the hydrophilic treatment of the above embodiment, the ratio of hydrochloric acid:hydrogen peroxide:water was set at 1:1:8; It is not limited to percentage. Also, instead of hydrochloric acid,
Ammonia (N I-T, OH), sulfuric acid (Hx SO
4), for example, NH, OI (: Ht
O,: l-1, O= I: 2: 7, H, SO
4:l-120! By setting as follows: H1O=5:l:4, it is possible to uniformly oxidize the surface of polycrystalline silicon film 2 while cleaning and removing particles.

Furthermore, in the above example, PCIt plasma etching was performed as dry etching, but RI
E (Reactive Ion Etching) and r
(IBE(Peactive Ion BearQEt)
(changing) etc. may also be performed.

FIGS. 3A to 3D are cross-sectional views showing an example in which the present invention is applied to a step of forming an element isolation region.

First, as shown in FIG. 3A, for example, the surface of a p-type silicon substrate IO is thermally oxidized to form a 5iOy film 11, and then a polycrystalline silicon film 12 and a Si3N4 film are sequentially formed on this SiO* film 11 by CVD. A film 13 is formed. Next, a photoresist 14 is selectively formed on this 5iaN4 film 13.

Next, the S+sN4 film 13 is etched by RIE using the photoresist I4 as a mask to form a 5isNa film 13a having a predetermined shape as shown in FIG. 3B, and the polycrystalline silicon film 12 is further etched to a predetermined thickness. Next, photoresist! After removing 4, Si, N, @1
3a as a mask, a p-type impurity such as boron (B) is added to the polycrystalline silicon film 12 and the SIO! Ions are implanted into the silicon substrate 10 through the film 11.

Next, by thermally oxidizing the polycrystalline silicon pa12 and the silicon substrate IO using, for example, the 5t3Ni film 13a as a mask, a thick 5ins film 1 is formed as shown in FIG. 3C.
5 (field oxide film) is formed.

Next, the 5isN4 film 13a is removed by wet etching using phosphoric acid (I(3PO4)), and then the polycrystalline silicon film 12a is etched by applying the present invention. This has the effect of preventing the formation of etching residue of crystalline silicon and preventing the occurrence of device defects.

[Effects of the Invention] As is clear from the above explanation, the polycrystalline silicon etching method according to the present invention allows polycrystalline silicon to be easily etched without paying attention to the water washing time or the wafer pulling speed in the water washing process. Since the surface of the film is made hydrophilic, it is effective in preventing the formation of water marks and etching residue of polycrystalline silicon.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the polycrystalline silicon etching method according to the present invention, FIGS. 2A to 2C are cross-sectional views thereof, and FIGS. 3A to 3D are process diagrams showing the process of forming an element isolation region according to the present invention. FIGS. 4A to 4C are cross-sectional views showing a conventional example. l...Insulating film, 2...Polycrystalline silicon film, 3...5
iOz membrane. Fig. 1 Practical example Fig. 2 A Pricing Fig. 28 Practical example Fig. 20 Fig. 3 A Fig. 3 B Fig. 3 D

Claims (1)

[Claims] (1) A method for etching polycrystalline silicon, which comprises treating the surface of a polycrystalline silicon film with a solution containing hydrogen peroxide to make the surface hydrophilic, and then performing etching.