Method for photolytic etching of silicon dioxide

FIELD: microelectronics.

SUBSTANCE: proposed method that can be used for photolytic etching of wafers in the course of manufacture of very large-scale integrated circuit includes etching of SiO2 surface in sulfur hexafluoride under action of vacuum ultraviolet emission of deuterium-vapor lamp. Argon is introduced in addition into etching gas.

EFFECT: enhanced selectivity of silicon dioxide etching with respect to monocrystalline and polycrystalline silicon.

3 cl, 1 tbl

 

The scope of the invention is microelectronics, namely the methods of dry etching the surface of the wafer during fabrication of very large scale integrated circuits (VLSI).

The known method photolytic etching of thin layers (10-20) chemically derived silicon dioxide (SiO2) chlorine TRIFLUORIDE (CIF3) when exposed to ultraviolet radiation from mercury sources low and medium pressure [1]. The process occurs in a flow of nitrogen at a pressure of 0.5-10 Torr and a temperature of 50-150°C. the Disadvantage of this method is the extremely low speed etching of the layer of thermal silicon dioxide even at elevated temperatures and pressures, and lack of selectivity of etching to the silicon, since the latter is etched in lF3even in the absence of ultraviolet radiation at a rate greater than the etching rate of the SiO2dozens of times. In addition, the disadvantages of this method of etching include high chemical aggressiveness and toxicity of the used reagent.

Closest to the proposed method is a method photolytic etching of polycrystalline silicon (Si*) sulphur hexafluoride (SF6) when exposed to vacuum ultraviolet radiation (VUV) from the deuterium lamp (D2- lamp) [2]. The disadvantages of this innovation is on the way is the lack of selectivity of etching of SiO 2with respect to Si, i.e. both layers are etched to about the same speed.

The task to be solved by the invention is the achievement of the technical result consists in increasing the selectivity of etching of SiO2with respect to Si, i.e. speeding etching of silicon dioxide with respect to the speed of etching of silicon. This technical result is achieved in the way photolytic etching of silicon dioxide, comprising the process of etching the surface of SiO2in the gas mixture of sulfur hexafluoride (SF6) with argon (ar), when exposed to VUV radiation from the D2-lamp. Moreover, the percentage of sulfur hexafluoride in the etching mixture is in the range from 50 to 10 vol.%, the percentage of argon in the range of 50 to 90 vol.%, and the etching process is performed at a pressure in the reaction chamber from 0.01 to 1.0 ATM.

Thus, the hallmark of the invention is to conduct the photolytic etching of silicon dioxide in a mixture of sulfur hexafluoride and argon. This distinctive feature makes it possible to achieve the technical result consists in increasing the selectivity of etching of SiO2with respect to Si.

It is possible that the process photolytic etching of silicon dioxide is as follows. Behavior is knosti of silicon dioxide and silicon adsorb SF 6and AG. The presence of AG promotes the penetration of quantum vacuum ultraviolet radiation to the substrate through absorbing their gas environment. Under the influence of VUV radiation adsorbed molecules break down into radicals education to be active against poison layers of particles and polymers, blocking etching. Moreover, the stability of such polymer films to the effects of vacuum ultraviolet radiation on the surface of the silicon and silicon dioxide are different, which leads to high selectivity of the process photolytic etching.

Examples of implementation of the method.

Prepared for photolytic etching plate with a layer of silicon dioxide was processed in a mixture gas of sulfur hexafluoride and argon when exposed to vacuum ultraviolet radiation from the deuterium lamp with a wavelength of 110-165 nm.

The experiments were conducted at room temperature and atmospheric pressure in the chamber and time VUV exposure from 5 to 20 minutes table 1 shows the main results of the conducted experiments.

Table 1
The dependence of the selectivity of etching of SiO2from process parameters
No.The composition of the etching gasPressure, ATMThe speed of travel is of SiO 2nm/minThe etching rate of Si, nm/minSelectivity SiO2: Si
 SF6,volume%Ar,% volume    
1100010,90,751,2:1
2802019,61,28:1
350501161,312:1
43070114,60,916:1
52080113,20,815:1
630700,010,750,0515:1

LITERATURE

[1]. D.C.Gray, W.Butterbaugh, .Fred Brian Harvey, A.Scott Lowing, H.H.Sawin. Photochemical Dry Etching of Doped and Undoped Silicon Oxides // J.Electrochem. Soc., 1995, v.142. No.11, R-3863.

[2]. W.Seiichi, U.Shinjirou, n.Norio, Timko. Photolytic etching of polycrystalline silicon in SF6 atmosphere. // Jap.J.Appl.Phys., 1986, Pt.2, v.25, No. 11, p.881-884.

1. The way photolytic etching of silicon dioxide (SiO2), comprising etching the surface of SiO2in the sulphur hexafluoride (SF 6) when exposed to vacuum ultraviolet radiation (VUV) from the deuterium lamp, characterized in that the etching gas is additionally introduced argon (Ar).

2. The method according to claim 1, characterized in that the percentage of sulfur hexafluoride in the etching mixture is within 50-10%, and the percentage of argon in the range 50-90%vol.

3. The method according to claims 1 and 2, characterized in that the etching is performed at a pressure in the reaction chamber of 0.01-1.0 ATM.



 

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