Semiconductor device structure including high voltage MOS device

This application is a divisional application of and claims the priority benefit of U.S. application Ser. No. 14/993,623, filed on Jan. 12, 2016, now allowed. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

This invention relates to a semiconductor process, and particularly relates to a method for fabricating a semiconductor device structure, and to a semiconductor device structure that can be formed with the same method.

Some kinds of integrated circuits include high-voltage (HV) MOS devices, such as Input/Output (JO) devices, for high-voltage operations. Since the operation voltage is high, an HV device requires a thick gate oxide layer.

However, the thick gate oxide layer is so thick that the uniformity of the shallow source/drain (S/D) junction formed by ion implantation through the gate oxide layer is reduced, so that the variation of breakdown voltage of the HV device is large.

Accordingly, this invention provides a method for fabricating a semiconductor device structure, which is capable of reducing the variation of the breakdown voltage of an HV MOS device.

This invention also provides a semiconductor device structure that can be formed with the fabrication method of this invention.

The fabrication method of this invention is described below. A first gate dielectric layer is formed on a substrate. A portion of the first gate dielectric layer, which is located on a part of the substrate in which a first S/D region is to be formed, is removed. A first gate electrode is formed on the remaining first gate dielectric layer. A spacer is formed on the sidewall of the first gate electrode and the sidewall of the remaining first gate dielectric layer. The first S/D region is then formed in the part of the substrate beside the first spacer. The first gate dielectric layer, the first gate electrode, the first spacer and the first S/D region belong to a first MOS device.

The semiconductor device structure of this invention includes a first gate dielectric layer on a substrate, a first gate electrode on the first gate dielectric layer, a first spacer on the sidewall of the first gate electrode and the sidewall of the first gate dielectric layer, and a first S/D region in the substrate beside the first spacer.

In an embodiment, the first MOS device is a high-voltage device.

In an embodiment, the first MOS device is formed simultaneously with a second MOS device that comprises a second gate dielectric layer, a second gate electrode, a second spacer and a second source/drain region. It is possible that the first MOS device is an HV device and the second MOS device a low-voltage (LV) device.

As this invention is applied to an HV MOS device, since the portion of the thick gate dielectric layer that is located on the part of the substrate to be formed with the first S/D region therein is removed in advance, the implantation of the first S/D region does not pass through the thick gate dielectric layer, so that the uniformity of the shallow S/D junction is reduced and the variation of breakdown voltage of the HV device is reduced.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below.

FIGS. 1, 2, 3, 4, 5 and 6 illustrate, in a cross-sectional view, a method for fabricating a semiconductor device structure according to an embodiment of this invention, wherein FIG. 6 also illustrates the structure of the semiconductor device structure according to the embodiment.

FIG. 2A illustrates, in a top view, a local structure of the patterned mask layer used in the step illustrated in FIG. 2 .

This invention will be further explained with the following embodiment and the accompanying drawings, which are not intended to restrict the scope of this invention. For example, although in the illustrated embodiment the first MOS device is an HV device that is formed simultaneously with a second MOS device being an LV device, this invention can also be applied to a case where the first MOS device is another kind of MOS device whose gate dielectric layer would affect the uniformity of the S/D junctions thereof, or a case forming only HV devices.

FIGS. 1, 2, 3, 4, 5 and 6 illustrate, in a cross-sectional view, a method for fabricating a semiconductor device structure according to an embodiment of this invention, wherein FIG. 6 also illustrates the structure of the semiconductor device structure according to the embodiment. FIG. 2A illustrates, in a top view, a local structure of the patterned mask layer used in the step illustrated in FIG. 2 , wherein the local structure is in the area of the first MOS device as a HV device.

Referring to FIG. 1 , a semiconductor substrate 100 is provided, having a first area 10 for an HV MOS device and a second area 20 for an LV MOS device, and having an isolation structure 102 therein. It is possible that the HV device is an input/output (JO) device and the LV device is a core device.

Source/drain extension regions 104 of the HV MOS device are formed in the substrate 100 in the first area 10 , using a correspondingly patterned mask layer (not shown). A thick gate dielectric layer 106 a of the HV device is then formed on the substrate 100 in the first area 10 , while a dielectric layer 106 b of the same material and thickness is formed on the substrate 100 in the second area 20 . To match the high operation voltage, the thick gate dielectric layer 106 a of the HV device has a thickness of, for example, 100 to 1200 angstroms. The gate dielectric layer 106 a may include a gate oxide layer, for example.

Referring to FIGS. 2 and 2A , the gate dielectric layer 106 a of the HV device is patterned to remove a portion thereof that is located on a part of the substrate 100 in which the source/drain regions of the HV device are to be formed, while the dielectric layer 106 b in the second area 20 for the LV device is entirely removed.

The mask pattern for patterning the gate dielectric layer 106 a is designed such that the remaining gate dielectric layer 106 c has a width larger than that of the gate electrode to be formed later. As shown in FIG. 2A with line A-A′ corresponding to the cross section view of FIG. 2 , the patterned mask layer 108 is designed to have openings 110 therein exposing the portions of the gate dielectric layer 106 a to be removed, and the portion of the gate dielectric layer 106 a covered by the patterned mask layer 108 , i.e., the portion to be made into the patterned gate dielectric layer 106 c later, has a width W 1 larger than the predetermined width W 2 of the gate electrode G to be formed later.

Referring to FIG. 3 , a thin gate dielectric layer 112 b of the LV device is then formed on the substrate 100 in the second area 20 for the LV device, while a thin dielectric layer 112 a of the same material and thickness is formed on the substrate 100 in the first area 10 for the HV device. The thin gate dielectric layer 112 b of the LV device has a thickness of, for example, 15 to 100 angstroms. The gate dielectric layer 112 b may include a gate oxide layer, for example.

Thereafter, a gate electrode 114 a of the HV device is formed on the thick gate dielectric layer 106 c in the first area 10 for the HV device, while a gate electrode 114 b of the same material and thickness of the LV device is formed on the thin gate dielectric layer 112 b in the second area 20 for the LV device. The material of the gate electrodes 114 a and 114 b may be doped polysilicon, for example.

Referring to FIG. 4 , S/D extension regions 116 of the LV device are formed in the substrate 100 beside the gate electrode 114 b of the LV device in the second area 20 , using a patterned mask layer (not shown) covering the first area 10 for the HV device.

Referring to FIG. 5 , a spacer 124 is formed on the sidewall of the gate electrode 114 a of the HV device and the sidewall of the thick gate dielectric layer 106 c in the first area 10 , and also on the sidewall of the gate electrode 114 b of the LV device in the second area 20 . The spacer 124 may be, for example, an ONO composite spacer that includes a silicon oxide layer 118 nearest to the sidewall of the gate electrode 114 a or 114 b , a silicon nitride layer 120 on the sidewall of the silicon oxide layer 118 , and another silicon oxide layer 122 on the sidewall of the silicon nitride layer 120 . A cleaning treatment may be performed then for the process of the spacer 124 , wherein the thin gate dielectric layer 112 b not covered by the gate electrode 114 b and the spacer 124 in the second area 20 and the thin dielectric layer 112 a not covered by the spacer 124 in the first area 10 may be removed, as shown in FIG. 5 .

Referring to FIG. 6 , S/D regions 130 a of the HV device are formed, with ion implantation, in the substrate 100 beside the spacer 124 in the first area 10 for the HV device, while S/D regions 130 b of the LV device are formed in the same manner in the substrate 100 beside the spacer 124 in the second area 20 for the LV device.

Since the portion of the thick gate dielectric layer 106 a that is located on the part of the substrate to be formed with the S/D regions 130 a of the HV device therein is removed in advance, the ion implantation of the S/D regions 130 a of the HV device does not pass through the thick gate dielectric layer 106 a , so that the uniformity of the shallow S/D junction of the HV device is reduced and the variation of the breakdown voltage of the HV device is reduced.

This invention has been disclosed above in the preferred embodiments, but is not limited to those. It is known to persons skilled in the art that some modifications and innovations may be made without departing from the spirit and scope of this invention. Hence, the scope of this invention should be defined by the following claims.