KR950004971B1 - Cleaning method of semiconductor device - Google Patents

Abstract

The method includes the steps of etching the oxide film on the silicon substrate to expose the silicon substrate, and etching the substrate to an etching depth of 30-200 angstrom by using the mixed gases of CHF series gas and O2 plasma gas, i.e. CF4/O2 plasma or HBr/Cl2 plasma gases thereby removing the residuals by a two-step cleaning process to improve the thermal oxidation of the wafer and reduce the junction leakage.

Description

How to remove residue after dry oxide etching

1 is a residue spectra characteristic diagram after general oxide overetch.

2 is a residue spectra characteristic diagram after dry cleaning according to the present invention.

3 is a residue spectra characteristic diagram after dry + wet cleaning according to the present invention.

4 is a minority carrier lifetime characteristic diagram in accordance with the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method during a semiconductor device manufacturing process, and more particularly, to a two-step cleaning method that is suitable for removing residues after dry cleaning when an oxide film is exposed to a silicon substrate.

In general, oxide etching in a semiconductor manufacturing process is used at the time of exposing a silicon substrate for forming an electrical contact, and an overetch process is often accompanied to more perfect the oxide film on the exposed silicon surface.

Etching chemicals used for etching the oxide film are inert carbon (Pluoro Carbon) -based plasma (Plasma) state.

Therefore, the fluorinated carbon polymer (Polymer) is left on the silicon surface exposed by the etching chemical and the reaction mechanism (mechanism) and the silicon substrate is damaged (demage). Such an oxide etch residue has a negative effect on device characteristics by preventing the thermal oxide formation process in the subsequent process and increasing the junction leakage. In order to remove the oxide etch residues, an operation for accurate analysis of the residues is currently underway. As it turns out, CFx polymer is present and SiO ₂ and SiC are formed under it.

Thus, there are O ₂ ashing and O ₂ annealing methods to remove the oxide etching residues to improve the electrical properties. (See, Struck, HP etal; Journal of Electrochemical Society, 135, P2876 (1988)) However, the application of O ₂ annealing or O ₂ ashing to remove residues removes most of the CFx-polymer but little of the remaining residues. The reason for this is that the exact identification of the chemical composition of the oxide etch residue is not made.

Therefore, after the etching of the oxide, the residue was accurately measured by X-Ray Photoelectro Spectroscope, and the result was not known (CFx-polymer / SiO ₂ / SiC / Si-substrate) but the structure (CFx-polymer / SiOyCz / Si-substrate) structure.

The result is shown in FIG.

That is, FIG. 1 (a) shows the overall spectrum FIG. 2 (b) is diagram showing the F _1S peak in detail represents the Si _2P peaks in detail FIG. 1 (C) C _1S peak second. Thus, residues identified in the prior art, the chemical composition H ₂ S _O4 -H _2O2 mixture or H ₂ S _O4 -O ₃ mixture, NH ₄₀ HH ₂₀₂ -H dry etch _20, such as a solution and HF solution, or BOE (Buffered Oxide Etchant) And wet etch.

As a result, the CFx-polymer is removed but the SiOyCz layer is not removed at all, so that the residue (SiOyCz) serves as an oxide growth blocking block in the subsequent thermal oxidation process, thereby increasing the minority carrier lifetime rigidity and junction leakage of the silicon substrate. There is a problem that acts to lower the device characteristics.

An object of the present invention is to provide a method for removing a residue that can completely remove the residue due to the oxide film etched to solve such a problem.

The present invention removes the SiOyCz layer from the residue after etching the oxide layer using a silicon etched knife such as CF ₄ / O ₂ plasma or HBr / Cl ₂ plasma, which is a mixture of CHF series and O ₂ .

When described in more detail with reference to the accompanying drawings, the present invention as follows.

First, when using a CF ₄ / O ₂ plasma increasing the O ₂ amount than CF ₄ SiOyCz layer

Scheme 1

The silicon layer that is mainly removed and damaged by reacting as in Equation (1)

Scheme 2

Scheme 3

The damage is removed by the same path as in Equation (2) and (3). When CF ₄ / O ₂ is used, not only the residue after the oxide film is etched but also the damage of the silicon substrate can be removed. In addition, when using HBr / Cl ₂ plasma

Scheme 4

As shown in Equation (4), the residue is removed by lift-off mainly due to the removal of the silicon layer, but the silicon damage itself is not so removed.

In order to prove the results of the present invention, FIG. 2 is an XPS spectra characteristic diagram of dry cleaning and FIG. 3 is an XPS spectra characteristic diagram after dry and wet cleaning.

That is, FIG. 2 (a) is a cleaning result by the O ₂ plasma and the second view (b) is a HBr / Cl ₂ dry cleaning results, the polymer CFx- 1 shown in Fig. (C) is O ₂ plasma or It is also removed by UV / O ₃ cleaning, but the SiOyCz layer shown in FIG. 1 (b) is not removed.

On the other hand, it can be seen that in the dry cleaning of CF ₄ / O ₂ or HBr / Cl ₂ , the SiOyCz layer is also removed. In addition, Figure 3 (a) shows the dry + wet cleaning results of O ₂ plasma + HF, Figure 3 (b) Figure 3 (b) shows the dry + wet cleaning results of UV / O ₃ + HF. , FIG. 3 (c) is a dry + wet cleaning results of the CF ₄ / O ₂ + SC1 + HF, FIG. 3 (d) is O ₂ plasma shows an dry + wet cleaning result of HBr / Cl ₂ + HF Dry + wet cleaning of + HF and UV / O ₃ + HF removes CFx-polymer but not SiOyCz layer, while dry + wet of CF ₄ / O ₂ + SC ₁ + HF and HBr / Cl ₂ + HF In the cleaning method, CFy-polymer as well as SiOyCz was removed.

Here, an oxide film (approx. 20 μs) is formed even after CF ₄ / O ₂ plasma or HBr / Cl ₂ plasma cleaning, so that the BOE or HF wet process completely removes residues and processes CF ₄ O ₂ plasma rather than HBr / Cl _2. More practical in terms of application, in which case the Silicon Etch Target should be adjusted from 30Å-300Å.

On the other hand, Figure 4 shows the carrier life time, so that the recovery of the life time can be obtained at the time of CF ₄ / O plasma cleaning.

As described above, in the method of removing residues after etching the oxide film of the present invention, as shown in Tables 1 and 2, the thermal oxidation of the wafer is well performed and the junction solution is reduced by wet etching (85%), which is a characteristic of the semiconductor device. Has the effect of improving.

TABLE 1

TABLE 2

Claims (5)

A method of removing residues after dry etching of an oxide layer, characterized in that the oxide layer is etched so that a silicon substrate is formed and then the residue is removed by etching with a hop gas of CHF series and O ₂ plasma. 2. The method of claim 1, wherein the amount of O ₂ is greater than that of the CHF series. The method of claim 1, wherein the depth of the etch is 30 to 200 microns. The method of claim 1, wherein the residue is removed after dry etching by etching with hydrofluoric acid (BOE) or HF solution. The method of claim 1, wherein the residue is etched with HBr / Cl ₂ plasma mixed gas.