Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-02-06
2001-02-27
Meeks, Timothy (Department: 1762)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S685000, C427S255230, C427S253000, C427S255280, C427S299000, C427S300000
Reexamination Certificate
active
06194314
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process for layer production on a surface, in particular a process for layer production on a surface of a semiconductor product.
The manufacture of semiconductor products, in particular of integrated semiconductor products, requires a complex sequence of individual steps. The manufacturing steps in which layers of material are produced on the surface of a semiconductor product assume an important role.
There are a number of processes available for the production of material layers, wherein processes in which the layers to be produced are deposited from the gaseous phase are the ones used most frequently. In particular chemical gaseous phase deposition (CVD=Chemical Vapor Deposition) is one of the most important processes for layer production. The basic principle of CVD is to conduct selected process gasses over a heated surface of a semiconductor product upon which the desired layer is intended to be deposited. A reaction of the process gasses occurs on the hot surface so that on one hand, the desired layer and on the other hand, remainder gasses that must be removed, are produced as reaction products.
The chemical gaseous phase deposition is usually carried out at low pressure in reaction chambers. The semiconductor products to be processed are fed into the reaction chamber and are heated to a predetermined temperature in the reaction chamber. Through the use of one or several gas inlets, the process gasses are supplied to the surface of the semiconductor product and the remainder gasses produced through the reaction of the process gasses are pumped out of the reaction chamber.
If a new semiconductor product is then fed into the reaction chamber for layer production, there is frequently the problem of there still being an aggressive gas in the reaction chamber from the preceding layer production process. That aggressive gas can be a remainder of a process gas used for layer production or it can be a remainder gas produced by the reaction of the process gasses. The aggressive gas can cause undesirable reactions on the surface of the semiconductor product, which damage the semiconductor product.
For example, in the production of tungsten layers, WF
6
is used as one of the process gasses. However, if WF
6
comes into contact with the surface of a Ti/TiN layer, which is used as a contact and barrier layer between silicon and tungsten, then undesirable reactions of WF
6
and titanium can occur:
WF
6
+Ti→W+TiF
x
.
Those kinds of reactions of WF
6
and titanium break down the Ti/TiN layer or impair the electrical properties (e.g. contact resistances) and can consequently jeopardize the functionality of the semiconductor product. Additionally, if WF
6
comes into contact with a silicon surface, an undesirable reaction can occur, which damages the silicon surface:
2WF
6
+3Si→2W+3SiF
4
.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a process for layer production on a surface, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known processes of this general type and in which damage to the surface by aggressive gasses is prevented.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for layer production on a surface, which comprises heating a surface to a predetermined temperature; supplying at least one first gas and at least one second gas reacting with the first gas, to the heated surface for layer deposition; and supplying at least one protective gas to the surface before and/or during the heating of the surface.
Through the use of the protective gas, on one hand, the aggressive gas still remaining in the reaction chamber is thinned and on the other hand, a part of the protective gas adsorbs onto the cold surface so that on the surface, preferably reactions of the aggressive gas with the protective gas occur and the surface layers themselves remain essentially undamaged. The protective gas is selected in such a way that in comparison to the atoms or molecules on the surface to be coated, it has a higher reactivity to the aggressive gas.
The invention can also be thought of as a process for protecting a surface during a process for layer production. The process for protecting a surface comprises supplying a protective gas to the surface before and/or during the heating of the surface.
In accordance with another mode of the invention, the protective gas is supplied to the surface together with a carrier gas, in particular argon.
It is furthermore preferable if the process for layer production is used to deposit a metallic layer, in particular a tungsten layer or a molybdenum layer.
In accordance with a further mode of the invention, at least one gas from the group of metal halogenides is selected as the first gas.
In accordance with an added mode of the invention, at least one gas from the group of silanes or hydrogen (H
2
) is selected as the second gas.
In accordance with an additional mode of the invention, a gas from the group of silanes, in particular silane (SiH
4
) is used as the protective gas.
In accordance with a concomitant mode of the invention, the process for layer production is carried out in a reaction chamber, and the protective gas is supplied to the surface at a location at which the product to be coated is fed into the reaction chamber. As a result, concentration of the aggressive gas can be reduced at this point without the throughput for the entire process being reduced.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process for layer production on a surface, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 5240505 (1993-08-01), Iwasaka et al.
patent: 5272112 (1993-12-01), Schmitz et al.
patent: 5316794 (1994-05-01), Carlson et al.
patent: 5342652 (1994-08-01), Foster et al.
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patent: 5599739 (1997-02-01), Merchant et al.
patent: 5686355 (1997-11-01), Sumi et al.
patent: 0416400A1 (1991-03-01), None
patent: 704551 (1996-04-01), None
patent: 0704551 A1 (1996-04-01), None
Publication in Electrochem. Soc., vol. 140, No. 2, dated Feb. 1993 (Saito K. et al.), pp. 513-518 “Selective Titanium Silicide Chemical Vapor Decomposition With Surface Cleaning by Silane and Ohmic Contact Formation to Very Shallow Junctions”.
Publication in Japanese Journal of Applied Physics dated Jan. 1990, No. 1, Part 2 (Saito K. et al.), pp. 185-187, “Effect of Silicon Surface Cleaning on the Initial Stage of Selective Titanium Silicide Chemical Vapor Deposition”.
Karcher Wolfram
Labs Lutz
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Meeks Timothy
Stemer Werner H.
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