Ion implantation process for forming contact regions in...

Details Ion implantation process for forming contact regions in... Ion implantation process for forming contact regions in...

1999-06-14

2001-06-12

Chaudhari, Chandra (Department: 2813)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S529000, C438S546000, C438S919000

Reexamination Certificate

active

06245608

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a semiconductor process, and more especially, to a method of an ion implantation for forming the contact areas in the semiconductor materials.
BACKGROUND OF THE INVENTION
In semiconductor industry, the conductive areas in a semiconductor material are generally formed of impurity-doped regions, such as source and drain regions of a metal-oxide semiconductor (MOS) transistor. The conductivity of such an impurity-doped region depends on the concentration of the impurities therein. The higher the concentration of the impurities is, the higher the conductivity of the doped region achieves.
In general, there are various devices, including N-type MOS (NMOS) transistors, P-type MOS (PMOS) transistors, and complementary MOS (CMOS) transistors, built on a semiconductor wafer. Different types of doped regions are formed in these devices with different carriers, wherein electrons are provided as carriers by N-type impurity dopants, and electric holes are provided as carriers by P-type impurity dopants. Specific contact regions in specific devices must be electrically interconnected so as to implement the whole desired circuit function. Normally, these contact regions are already doped conductive regions and serve as electrodes in those devices. However, when the integration of the wafer increases and the dimension of the device scales down, the original doped concentration for the devices' electrodes may no longer provide a sufficient conductivity for the contact regions. Therefore, a contact ion implantation must be carried out to increase the doped concentration of the contact regions.
FIG. 1
illustrates an example of a semiconductor wafer
2
that consists of various devices with doped regions of different conductive types. A twin-well CMOS device is shown with an N-well region
4
, a P-well region
6
, field oxide regions
8
, a PMOS device
10
, and an NMOS device
20
. A dielectric layer
30
, wherein contact holes
32
and
34
are opened to provide contact to the interconnecting lines, is formed on the wafer. Generally, contact holes
32
and
34
are formed aligned to the source and drain regions
14
and
24
of the transistors, which are already doped conductive regions. As mentioned above, the original doped concentration for the source and drain regions can no longer provide a sufficient contact conductivity. Therefore, a contact ion implantation must be carried out to form contact regions for the source and drain regions.
In a conventional manner as mentioned above, masks with different patterns are usually used in different types of ion implantation.
FIG. 2
illustrates the two mask patterns adopted for the example shown in FIG.
1
. For the contact ion implantation of P-type ions, an implantation mask
40
as shown in
FIG. 2A
are patterned on the wafer. The blanket P-type ion implantation and the mask removing are then performed in sequence to form the P-type contact regions
16
in the PMOS device. Thereafter, an implantation mask
42
as shown in
FIG. 2B
are patterned on the wafer. The blanket N-type ion implantation and the mask removing are subsequently performed to form the N-type contact regions
26
in the NMOS device. In this method, two mask patterning, and two masking removing must be carried out. The fabrication processes are complicate.
SUMMARY OF THE INVENTION
The present invention proposes a method of contact ion implantation to form different types of doped contact regions in the semiconductor substrate. This method utilized only one mask and a dosage-enhanced implantation to implement the contact ion implantation. The fabrication process for the doped contact regions of various conductive types can thus be simplified.
A semiconductor substrate having doped regions of different conductive types and a dielectric layer with contact holes is provided. A blanket ion implantation of the first conductive type is carried out, and all the contact regions of first conductive type and second conductive type are formed with the first conductive type impurities. Thereafter, a mask with the pattern that covers the designed first type contact regions and exposes the second type regions is defined. An ion implantation of the second conductive type is then carried out to implant impurity ions of second conductive type with an enhanced dosage into the contact regions designed for second conductive type. The dosage of these second conductive type ions is determined so that, after the implantation, the contact regions of the second conductive type have a total concentration of the first and second type impurities that can provide a preferable amount of carriers. After removing the implantation mask, the present process is completed.


REFERENCES:
patent: 4406710 (1983-09-01), Davies et al.
patent: 4420344 (1983-12-01), Davies et al.
patent: 4553315 (1985-11-01), McCarty
patent: 4956311 (1990-09-01), Liou et al.
patent: 5908309 (1999-06-01), Andoh

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