RU2008745C1 - Process of production of nitrided oxide layer on substrate of semiconductor material - Google Patents

Abstract

FIELD: semiconductor devices. SUBSTANCE: process includes formation of oxide layer on substrate and following thermal nitriding of it in nitrogen-containing gaseous atmosphere in electromagnetic radiation field which range of wave length is chosen from ionizing condition of atmosphere. EFFECT: improved electrophysical parameters and radiation stability with thickness of layer above.

Description

 The invention relates to microelectronics, in particular to the production technology of semiconductor devices and integrated circuits, and is intended to produce gate oxide layers of CMOS integrated circuits, semiconductor devices, and oxide layers used as insulation of active elements in integrated and discrete structures.

A known method of obtaining a radiation-resistant coating of silicon oxynitride [1], which consists in the fact that the film is deposited pyrolytically, followed by annealing in a hydrogen atmosphere at 500 ^about C for 3 hours

 However, this method does not allow to obtain a film with satisfactory electrical characteristics.

 Closest to the invention is a method for producing a nitrated oxide layer on a substrate of semiconductor material [2], which includes the formation of an oxide layer and its subsequent thermal nitration in a nitrogen-containing gas medium in the field of electromagnetic radiation.

 This method allows to obtain satisfactory electrophysical characteristics of the gate oxide, but is suitable only for ultrathin dielectric layers in CMOS circuits and does not provide good radiation resistance of the layer.

.The aim of the invention is to improve the electrophysical parameters and increase the radiation resistance of nitrated oxide layers with an increase in their thickness over 100

.

 To achieve the goal, the wavelength range of electromagnetic radiation is selected from the condition of ionization of a nitrogen-containing gas medium.

) до толстых (1 мкм и более) при пониженной температуре нитрирования (800-900^оС), что, в свою очередь, дает возможность увеличить значение и уменьшить разброс критической напряженности электрического поля в диэлектрике; уменьшить сдвиг порогового напряжения при воздействии ИИ с дозой 10⁶ рад в 2-3 раза, уменьшить величину изменения плотности поверхностных состояний на границе раздела Si - SiO₂ после воздействия ионизирующих излучений, а, следовательно, повысить радиационную стойкость диэлектрика за счет создания в его объеме центров, компенсирующих положительный заряд, образующийся после воздействия ИИ.During the ionization of nitrogen-containing gaseous media, nitrogen atoms are excited, their effective radius decreases, and their diffusion rate into the silicon dioxide layer increases. It becomes possible to effectively nitrate a silicon dioxide layer of a wide range of thicknesses, from ultrathin (100

) To thick (1 micron or more) at low temperature nitriding (800-900 ^C), which in turn makes it possible to increase the value and reduce dispersion of the critical electric field in the insulator; to reduce the threshold voltage shift under the action of AI with a dose of 10 ⁶ rad by a factor of 2–3, to reduce the change in the density of surface states at the Si – SiO ₂ interface after exposure to ionizing radiation, and, therefore, to increase the radiation resistance of the dielectric by creating in its volume centers that compensate for the positive charge formed after exposure to AI.

 Almost all nitrogen-containing gases decay into atoms and ionize in the field of gamma and x-ray radiation. Ultraviolet radiation acts in a similar way for wavelengths corresponding to the absorption bands of the gas used.

So, for NH ₃ absorption bands correspond to: 1st band 170-217 nm 2nd band 140-169 nm 3rd band 115-150 nm.

NH₂ ^*XB₁/ + H^* -λ≅ 280нм
NH₃

NH^*(a¹Δ ) + H₂ --λ≅ 2240 нм
NH₃

NH^*(x³ε ) + H^* + H^* ≅1470 нм.The process of activation and decomposition of a gas molecule into radicals can be represented as follows:
NH ₃

NH ₂ ^* XB ₁ / + H ^* -λ≅ 280nm
NH ₃

NH ^* (a ¹ Δ) + H ₂ --λ≅ 2240 nm
NH ₃

NH ^* (x ³ ε) + H ^* + H ^* ≅ 1470 nm.

NH₃ ^* +

- ионизация.NH ₃

NH ₃ ^* +

- ionization.

 For atomic and molecular nitrogen, the ionization process begins with λ = 85.0-65.0 nm, and the activation process with excitation with λ = 160-300 nm. Reducing the wavelength of ultraviolet radiation increases the likelihood of ionization, activation of gaseous media per unit time.

Example 1. Oxidize a p-type silicon wafer (100) to an oxide thickness of 350-450 ^° C, place it in a quartz tube of a diffusion furnace so that the nitrogen-containing gas flowing around the wafer is exposed to ultraviolet radiation (UV) near the surface plates on the side of the oxide layer.

Mode:
- oxidation temperature - 950 ^{° C;}
- nitriding temperature - 950 ^{° C;}
- process time - 5 min, loading, O ₂ gas (100 l / h), 20 min oxidation, the same gas, 10 min - N ₂ purge (150 l / h), 25 min - nitration, N ₂ gas (150 l / h), NH ₃ (15 l / h), UVI with λ = 180-600 nm, 5 min - unloading N ₂ (150 l / h).

Parameters of the resulting structures:
- critical electric field strength - E _cr = 1.15-1.3 x 10 ⁷ V / cm;
- shift of the threshold voltage ΔU ≅ 0.1 V;
- resistance to ionizing radiation - at a dose of D = 1.10 ⁶ p, the change in U _then less than 10%.

Окисленную пластину запаивают в кварцевую трубу, заполненную азотом с добавкой 5% NH₃. Давление в трубе составляет приблизительно 1 атм. Труба помещается в термопечь, находящуюся в установке МРХ γ-20 (изотоп Со⁶⁰).EXAMPLE Example 2 A silicon wafer is placed in a quartz tube diffusion furnace for oxidation: T = 950 ^C, gas - O ₂ (100 l / h), the oxide thickness - 350-450

The oxidized plate is sealed in a quartz tube filled with nitrogen with the addition of 5% NH ₃ . The pressure in the pipe is approximately 1 atm. The pipe is placed in a thermal furnace located in the MPX γ-20 installation (Co ⁶⁰ isotope).

Nitriding mode: T = 800 ^о С, t = 120 min.

Installation mode: E = 1.25 MeV; P = 180 P / s; t _arr. = 60 min.

Parameters of the resulting structures:
- E _cr = 10 ⁷ V / cm;
- threshold voltage shift напряжения 0.15 V;
- resistance to the effects of ionizing radiation - at a dose of D = 10 ⁶ r change in U _then ≅ 10%.

The special nature of the nitration operation, namely: thermal nitriding in the fields of ionizing radiation that activate the nitrogen-containing gas media used, allows to improve the electrophysical parameters of the nitrated silicon dioxide layer; increase the value and reduce the spread of the critical electric field in the dielectric layer; reduce the density of surface states at the Si - SiO ₂ interface to a value of the order of 5 ˙ ^{10 10} cm ^-2 ev ^-1 ; to increase the radiation resistance of the silicon dioxide layer.

The creation of negative charged centers in nitrated silicon dioxide effectively compensates for the charge arising from the action of AI up to dose values of 10 ⁶ -10 ⁷ rad for a wide range of silicon dioxide thicknesses. (56) 1. U.S. Patent No. 3,765,935, cl. B 44 d 1/18, publ. 1973.

 2. Fang Y. K. et al. "Inprovement of thin-gate oxide integrity using photoenhanced low-temperature nitridation" - Solid State Electronics, 1990, v. 33, No. 8, p. 1039-1041.

Claims (1)

METHOD FOR PRODUCING A NITRATED OXY LAYER ON A SUBSTRATE FROM SEMICONDUCTOR MATERIAL, including the formation of an oxide layer on a substrate and its subsequent thermal nitration in a nitrogen-containing gas medium in the field of electromagnetic radiation, characterized in that, in order to improve the electrophysical parameters and increase the radiation thickness at a thickness of 100

the wavelength range of electromagnetic radiation is selected from the condition of ionization of a nitrogen-containing gas medium.