RU237046U1 - CMOS IC with NMOS transistors - Google Patents

Abstract

The utility model is applied in the field of semiconductor device designs and integrated circuits with CMOS structures. The technical result of the utility model is a reduction in cost and simplification of the technological process of manufacturing N-MOS transistors in CMOS microcircuits. The specified technical result is achieved by the fact that, unlike the known ones, in a CMOS microcircuit with N-MOS transistors consisting of a silicon monocrystalline substrate of P-type conductivity, pockets of N-type conductivity for forming P-MOS transistors made by doping with phosphorus, guard regions of N-type conductivity formed in the pockets of N-type conductivity made by doping with phosphorus, source and drain regions of N-MOS transistors made by doping with arsenic, contact windows in a protective layer of phosphosilicate glass to the source and drain regions of N-MOS transistors, a layer of protection against dissolution of the source and drain regions of N-MOS transistors, aluminum metallization, the layer of protection against dissolution of the source and drain regions is made by doping with phosphorus the region of the contact windows of the source and drain during the formation of guard regions of N-type conductivity.

Description

The utility model is applied in the field of designs of semiconductor devices and integrated circuits with CMOS structures.

CMOS microcircuits with N-channel MOS transistors (N-MOS transistors) are known, consisting of a silicon substrate with P-type conductivity, guard regions, a silicon oxide layer, source and drain regions made by doping with arsenic, contact windows in the protective silicon oxide layer to the source and drain regions, a layer of protection against dissolution of the source and drain regions, aluminum metallization (see, for example, the book Widmann D. Technology of Integrated Circuits / D. Widmann, H. Mader, H. Friedrich. - Berlin: Springer, 1995. - p. 286-295).

The source and drain regions of N-MOS transistors made by doping with arsenic, as a rule, have a depth of no more than 0.2-0.3 μm, which allows to significantly increase the reproducibility of obtaining a stable channel length of N-MOS transistors and low resistances of these regions in comparison with the source and drain regions of N-MOS transistors made by doping with phosphorus. However, the source and drain regions of N-MOS transistors made by doping with arsenic to a small depth require a rather labor-intensive technological operation of forming a layer of protection against dissolution in aluminum metallization. The layer of protection against dissolution is formed by applying a layer of titanium silicide TiSi ₂ . In the absence of a protection layer, silicon doped with arsenic will dissolve in the aluminum metallization, as a result of which the metallization of the drain and source regions will be shorted to the substrate along the aluminum grains.

In addition, CMOS microcircuits are unstable to the thyristor effect.

The closest to a utility model is a CMOS microcircuit with N-MOS transistors, consisting of a silicon substrate with P-type conductivity, N-type conductivity pockets for forming P-MOS transistors made by doping with phosphorus, N-type conductivity guard regions formed in the N-type conductivity pockets, N-MOS transistor source and drain regions made by doping with phosphorus, contact windows in a protective layer of phosphosilicate glass to the source and drain regions of N-MOS transistors (see, for example, the book by Enns V. I., Kobzev Yu. M. Design of analog CMOS microcircuits. A brief developer's handbook / Edited by Cand. Sci. (Eng.) V. I. Enns. - M .: Goryachaya Liniya-Telecom. - 2005. - 454 p.: ill. 140).

N-type guard regions formed in N-type pockets for forming P-MOS transistors of CMOS microcircuits, made by doping with phosphorus, reduce the gain of parasitic transistors on which the thyristor effect is observed. In addition, they provide ohmic contact of the aluminum metallization with the pocket regions.

However, the source and drain regions of N-MOS transistors made by doping with phosphorus, as a rule, have a depth of at least 0.6-0.7 μm, which negatively affects the reproducibility of obtaining a stable channel length of transistors. In order to increase the reproducibility of obtaining a stable channel length, the source and drain regions of N-MOS transistors must be made by doping with arsenic, which will require a labor-intensive technological operation of forming a protective layer from dissolution of the source and drain regions in aluminum metallization from TiSi _2. This will lead to an increase in the cost and complexity of the technological process.

The technical result of the utility model is a reduction in cost and simplification of the technological process of manufacturing N-MOS transistors in CMOS microcircuits.

The specified technical result is achieved by the fact that, unlike the known ones, in a CMOS microcircuit with N-MOS transistors consisting of a silicon monocrystalline substrate of P-type conductivity, pockets of N-type conductivity for forming P-MOS transistors made by doping with phosphorus, guard regions of N-type conductivity formed in the pockets of N-type conductivity made by doping with phosphorus, source and drain regions of N-MOS transistors made by doping with arsenic, contact windows in a protective layer of phosphosilicate glass to the source and drain regions of N-MOS transistors, a layer of protection against dissolution of the source and drain regions of N-MOS transistors, aluminum metallization, the layer of protection against dissolution of the source and drain regions is made by doping with phosphorus the region of the contact windows of the source and drain during the formation of guard regions of N-type conductivity.

Since the depth of phosphorus doping of the dissolution protection layer of the source and drain regions is greater than the depth of arsenic doping of the source and drain regions of N-MOS transistors, when forming aluminum metallization in aluminum, deeper regions additionally doped with phosphorus will dissolve, and there will be no short-circuiting of the aluminum metallization of the drain and source regions to the substrate.

Since the formation of the channel length of N-MOS transistors involves the boundaries of the drain and source, which are made by doping with arsenic, doping the layer of protection against dissolution of the source and drain regions with phosphorus will not affect the reproducibility of obtaining a stable channel length of transistors.

The essence of the proposed utility model is explained in Fig. 1, which shows the design of a silicon semiconductor device (N-MOS transistor in a CMOS microcircuit) corresponding to the proposed utility model.

The positions in Fig. 1 indicate:

1 - silicon monocrystalline substrate with P-type conductivity;

2 - N-type conductivity pocket for forming R-MOS transistors, made by doping with phosphorus;

3 - N-type conductivity guard region, made by doping with phosphorus;

4 - a layer of protection against dissolution of the source and drain areas, made by doping the source and drain contact windows with phosphorus when forming protective areas of N-type conductivity;

5 - source and drain regions of N-MOS transistors, made by doping with arsenic;

6 - gate silicon oxide;

7 - polysilicon gate;

8 - aluminum metallization;

9 - protective layer of phosphosilicate glass (PGS).

The utility model (N-MOS transistor in a CMOS microcircuit) has the following design: in a silicon monocrystalline substrate of p-type conductivity 1 with a specific resistance of 12 Ohm-cm (see: Fig. 1), pockets of N-type conductivity were created for forming P-MOS transistors by doping with phosphorus 2 with an irradiation dose of D=0.6-0.8 μC/ ^cm2 and an ion energy of E=70 keV and by accelerating the phosphorus at a temperature of T=1200°C for 10 hours in a nitrogen atmosphere. Guard regions of N-type conductivity 3 were formed in the pockets of N-type conductivity by doping with phosphorus with a doping dose of D=300 μC/ ^cm2 and an ion energy of E=40 keV and by accelerating the phosphorus at a temperature of T=1000°C for 30 minutes in a nitrogen atmosphere. Simultaneously with the formation of the N-type conductivity guard regions, a layer of protection against dissolution of the source and drain regions 4 was created by doping the source and drain contact windows with phosphorus. Then, a layer of gate silicon oxide 6 with a thickness of 360 Å was created at a temperature of T = 850 °C and a polysilicon gate 7 with a thickness of d _poly-Si = 0.38-0.44 μm at a temperature of T = 650 °C. After that, the source and drain regions of the N-channel MOS transistors were formed by doping with arsenic 5 with a doping dose of D = 1000 μC/cm ² and an ion energy of E = 90 keV and accelerating arsenic at a temperature of T = 850 °C for 30 minutes in a nitrogen atmosphere. After forming a protective layer of phosphosilicate glass 9 with a thickness of 0.6-0.8 μm by deposition from the gas phase at a temperature of T=850°C and reduced pressure, holes were opened in it to create contact windows to the source and drain areas. Then, aluminum metallization 8 was formed on the plate by sputtering an Al-Si film with a thickness of d _A1 - 0.5-0.7 μm and photolithography.

Since the layer of protection against dissolution of the source and drain areas is made by doping the area of the contact windows of the source and drain with phosphorus during the formation of protective areas of N-type conductivity, there is no need to carry out additional technological operations to form a layer of protection against dissolution of the source and drain areas in aluminum metallization from TiSi ₂ : application of titanium silicide and photolithography.

The result of the utility model is a simplification of the technological process of manufacturing N-MOS transistors in CMOS microcircuits and a reduction in the cost of the process by 7% due to the elimination of additional operations.

Claims (1)

A CMOS microcircuit with N-MOS transistors, consisting of a silicon monocrystalline substrate with P-type conductivity, N-type conductivity pockets for forming P-MOS transistors, made by doping with phosphorus, N-type conductivity guard regions formed in the N-type conductivity pockets, made by doping with phosphorus, source and drain regions of N-MOS transistors made by doping with arsenic, contact windows in a protective layer of phosphosilicate glass to the source and drain regions of N-MOS transistors, a layer of protection against dissolution of the source and drain regions of N-MOS transistors, aluminum metallization, characterized in that the layer of protection against dissolution of the source and drain regions is made by doping with phosphorus the region of the source and drain contact windows during the formation of N-type conductivity guard regions.