JPS62136827A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To inhibit the etching of Si, and to improve a heavy-metal removal effect by forming a thin oxide film on the surface of an Si substrate prior to chlorine-gas treatment while irradiating the surface of the substrate by ultraviolet rays having a specific wavelength during treatment. CONSTITUTION:An SiO2 layer in 20-200Angstrom is shaped on the surface of an Si substrate prior to chlorine-gas treatment. When the SiO2 layer the Si substrate are positioned in a chlorine atmosphere, projecting ultraviolet rays having wavelengths of 180-400nm, Cl2 gas is dissociated directly, is changed into Cl radicals and is adsorbed to an SiO2 surface by conduction electrons transmitted by a tunnel phenomenon in SiO2, and reaches to the surface of the Si substrate by a diffusion, and Cl radicals and Si or a heavy metal are reacted. Cl radicals combine with the heavy metal in a bulk by such a reaction, and one part of the heavy metal is removed as a gas and one part is gettered. The reaction can be induced at a low temperature of 100-500 deg.C by ultraviolet exposure.

Description

[Detailed Description of the Invention] [Summary] In the chlorine gas treatment of the surface of the Si substrate, the Si surface layer is not etched (in order to remove and remove heavy metals in the Si substrate at low temperature, a thin layer is formed before the chlorine gas treatment). An oxide layer is provided on the surface of the Si substrate.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device,
More specifically, the present invention relates to improvements in the cleaning process, particularly the process of cleaning heavy metals with chlorine gas, in the process of manufacturing semiconductor devices using Si semiconductor substrates.

[Conventional technology]

Cleaning of Si semiconductor substrates has conventionally been carried out by wet cleaning, but there is a problem in that it is complicated because it requires several stages of processing. To solve this problem CA z
A method of cleaning using gas has been proposed. In this cleaning method, contaminants are removed by heating a Si semiconductor substrate, which has undergone a process of growing or depositing a thin oxide film, to 100 to 500°C in a Cez gas atmosphere.

[Problem that the invention attempts to explain]

Conventional Si contamination removal treatment using chlorine gas has the following problems.

(i) In cases where deep etching of Si occurs due to the progress of etching of Si with chlorine gas, the chlorine gas cleaning treatment method is not necessarily suitable as a pretreatment method for the Si substrate. In particular, when chlorine gas cleaning is performed as a pretreatment method for gate oxidation of MOS, etching occurs and unevenness is produced, resulting in unsatisfactory results.

(11) When the surface of the Si substrate to be etched by chlorine gas is observed, a thin blackened layer is observed. This blackened layer is a residue of an extremely low-density Si layer remaining on the surface to be etched, and is thought to be composed of ultrafine Si particles. Particularly when an n-type low resistance substrate is processed, a noticeable residue is observed. Therefore, some kind of cleaning process is subsequently required.

(iii) The range of applicable etching processing conditions, particularly substrate temperature, is narrow, and therefore the expected effects are also limited.

(iv) Since the etching speed varies significantly depending on the specific resistance of the Si substrate, if regions with different specific resistances are provided on the same substrate, the etching effect will differ on the same substrate and the expected effect will be limited. be done.

[Means for solving problems]

The feature of the present invention is that the S
It consists of a combination of treating the surface of the i-substrate and forming a thin oxide layer as a pretreatment. When a Si substrate is placed in a chlorine atmosphere having a pressure of preferably 10 to 100 Torr, the substrate temperature is set at a low temperature of 100 to 500° C., and ultraviolet rays are irradiated, Si etching occurs. However, the reaction between Si and chlorine has the following problems. That is, some of the heavy metals in the bulk beneath the surface of the Si to be etched are removed as gas and some are locally collected. By the way, when processing a substrate through such Si etching, it is necessary to
There are various constraints associated with the substrate, and since the phenomenon of etching is utilized, sufficient diffusion of C1 into the substrate does not occur, which limits the effectiveness of substrate processing (heavy metal removal).

According to the present invention, a thin Si02 layer is provided on the surface of the Si substrate prior to chlorine gas treatment. 5i02 is not etched by chlorine radicals, but when the Sing layer/St substrate is irradiated with ultraviolet light (wavelength shorter than 4000 . . .), conduction electrons are excited in Si. Therefore, when the Sing layer/Si substrate is placed in a chlorine atmosphere while being irradiated with ultraviolet rays, CZ and gas are directly dissociated by the ultraviolet irradiation, resulting in C7! The Cl radicals become radicals and are adsorbed on the 5in2 surface by conduction electrons transmitted through SiOg by tunneling, and further reach the Si substrate surface by diffusion, where a reaction between the Cl radicals and Si or heavy metals occurs. Through this reaction, Cl radicals combine with heavy metals in the bulk, and some of the heavy metals are removed as gas and some of them are gettered. This reaction was stimulated by ultraviolet irradiation to 100%
It can be induced at low temperatures of ~500°C.

As mentioned above, the desired results can be achieved by UV irradiation and the formation of an oxide layer. Here, the thickness of the oxide layer is 2
The reason for setting the number to 0 to 200 is that the effect of the present invention cannot be achieved outside this range, and the wavelength of ultraviolet rays is set to 180 to 200.
The reason why the thickness is set to 400 nm is that the dissociation of chlorine gas and the excitation of Si conduction electrons are effectively performed. The method for forming the oxide layer is C.
Any method such as VD or thermal oxidation may be used.

[For production]

By providing the SiO□ layer in advance as described above, the Si
(i) gettering and bonding with heavy metals proceed preferentially over etching, allowing long-term chlorine gas treatment; (ii) no residue is generated; and (iii) 34 Chlorine gas treatment can now be applied even when the substrate has different resistivity regions.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

In the figure, 1 is an Hg lamp, 2 is an ultraviolet selective reflection mirror, 3 is a bell jar, 4 is a synthetic quartz window, 5 is a heater, 6 is an exhaust port connected to a vacuum pump, and 7 is a carrier gas for chlorine gas (
Inert gas) and also.

is a supply port that supplies only chlorine gas.

The treatment was carried out under the following conditions.

CI-z pressure -50Torr (100% C12 gas)
Clz flow it 15sec Ultraviolet wavelength - 290~370nm Ultraviolet intensity - 800mW/cm 2 substrate-window distance - 5cm 5iO□ layer - 30 people (1000℃ dry oxidation) Processing time - 60 minutes Substrate temperature - 300℃ Above treatment Thereafter, an Ae electrode was formed by dry oxidation to an oxide film thickness of 100 oxides. The generation lifetime of minority carriers measured by C- is ~100 μsec on an untreated substrate ~
The time was improved to 200μsec.

〔Effect of the invention〕

By depositing or growing a thin oxide film before photoexcited chlorine treatment of the Si substrate, etching of 3i can be suppressed and heavy metal removal effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an example of an apparatus for carrying out the surface treatment method of the present invention. DESCRIPTION OF SYMBOLS 1... Hg lamp, 2... Ultraviolet selective reflection mirror, 3... Bell jar, 4... Synthetic quartz window, 5... Resistance heater, 6... Vacuum exhaust port, 7... Gas supply port.

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device that involves surface treatment of a Si substrate using chlorine gas, 20 to 200
1. A method for manufacturing a semiconductor device, which comprises growing or depositing an oxide layer of 1.5 Å on the surface of a Si substrate, and irradiating ultraviolet light of 180 to 400 nm during processing.