SiGe MOSFET with an erosion preventing Six1Gey1 layer

1. Field of the Invention

The present invention relates to a structure of an integrated circuit (IC) device, and more particularly, to a semiconductor device.

2. Description of the Related Art

Once the gate length of the silicon metal-oxide semiconductor (MOS) transistor device is reduced to a deep submicron range, because the carrier passing time decreases along with the decrease of the channel length, a device with better performance is obtained. However, many problems still need to be solved in the aspect of fabricating technique thereof. For example, when the device is becoming smaller, the size of the source/drain area reduces accordingly, which increases the contact resistance of the source/drain terminal, thus the device fails to maintain the original high current driving capability.

In order to resolve the problem mentioned above, a silicon-germanium (Si x Ge y ) technique has been developed for fabricating an MOS transistor with raised source/drain. Since the silicon-germanium can be selectively grown in the source/drain area as well as selectively etched compared to silicon and silicon oxide, silicon-germanium is a more suitable material for fabricating semiconductor devices compared to silicon. Moreover, since silicon-germanium has a lower energy width than that of silicon, a lower schottky barrier height is existed on the p-type junction, which reduces the contact resistance.

However, the MOS transistor with raised source/drain fabricated by the silicon-germanium technique is likely to cause problems such as film damages during the subsequent fabricating process, for example, in the subsequent cleaning process. Consequently, the reliability of the fabricating process is affected.

Therefore, it is an object of the present invention to provide a semiconductor device which prevents the raised source/drain film from being worn down or damaged, thus the reliability of the fabricating process and the device performance are not impacted.

It is another object of the present invention to provide another semiconductor device which prevents the raised source/drain film from being worn down or damaged, thus the reliability of the fabricating process and the device performance are not impacted.

The present invention provides a semiconductor device which comprises a substrate, a gate structure, a spacer, a Si x Ge y layer and a Si x Ge y protection layer. The gate structure is deposited on the substrate and the spacer is deposited on the sidewalls of the gate structure. The Si x Ge y layer is deposited in the substrate on both sides of the spacer and extended to a portion beneath part of the spacer. In addition, the top level of the Si x Ge y layer is higher than the surface of the substrate. Moreover, the Si x Ge y protection layer is deposited on the Si x Ge y layer and the Si x Ge y protection layer comprises Si x Ge y , where 0≦y1<y.

In accordance with an embodiment of the present invention, the semiconductor device mentioned above further comprises a metal silicide layer. The metal silicide layer is deposited in part of the Si x Ge y protection layer and on the gate structure, wherein the thickness ratio of the metal silicide layer and the Si x Ge y protection layer is between 0.5˜1.0. The material of the metal silicide layer is a refractory metal silicide, for example, and the refractory metal is selected from a group consisting of Ti (titanium), W (tungsten), Pt (platinum), Co (cobalt) and Ni (nickel).

The present invention further provides another semiconductor device. The semiconductor device comprises a substrate, a gate structure, a spacer, a Si x Ge y B z layer and a Si x Ge y B z protection layer. The gate structure is deposited on the substrate, and the spacer is deposited on the sidewalls of the gate structure. The Si x Ge y B z layer is deposited in the substrate on both sides of the spacer and extended to a portion beneath part of the spacer. In addition, the top level of the Si x Ge y B z layer is higher than the surface of the substrate. Moreover, the Si x Ge y B z protection layer is deposited on the Si x Ge y B z layer and the Si x Ge y B z protection layer comprises Si x1 Ge y1 B z1 , where 0<y1<y and 0<z1<z.

In accordance with an embodiment of the present invention, the semiconductor device mentioned above further comprises a metal silicide layer. The metal silicide layer is deposited in part of the Si x Ge y B z protection layer and on the gate structure, wherein the thickness ratio of the metal silicide layer and the Si x Ge y B z protection layer is between 0.5˜1.0. The material of the metal silicide layer is a refractory metal silicide, for example, and the refractory metal is selected from a group consisting of Ti (titanium), W (tungsten), Pt (platinum), Co (cobalt) and Ni (nickel).

In accordance with an embodiment of the present invention, the concentration of boron (B) in the Si x Ge y B z layer is between 5×10 19 ˜5×10 20 atoms/cm 3 .

A Si x Ge y protection layer or a Si x Ge y B z protection layer is deposited in the semiconductor device of the present invention, which prevents the film underneath the Si x Ge y layer or the Si x Ge y B z layer from being worn down or damaged, thus the reliability of the fabricating process and the device performance are not impacted. In addition, the content of Ge (germanium) in the Si x Ge y protection layer or the Si x Ge y B z protection layer is lower than the content of Ge (germanium) in the Si x Ge y layer or the Si x Ge y B z layer that the etch rate of the subsequent cleaning process is slowed down and the underneath Si x Ge y layer or the Si x Ge y B z layer is prevented from being eroded. On the other hand, a metal silicide layer may be formed by the Si x Ge y protection layer or the Si x Ge y B z protection layer, which also prevents the underneath Si x Ge y layer or the Si x Ge y B z layer from being worn down.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.

FIG. 1 schematically shows a cross-sectional view of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 schematically shows a cross-sectional view of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 schematically shows a cross-sectional view of a semiconductor device according to a third embodiment of the present invention.

FIG. 4 schematically shows a cross-sectional view of a semiconductor device according to a fourth embodiment of the present invention.

FIG. 1 schematically shows a cross-sectional view of a semiconductor device according to a first embodiment of the present invention.

Referring to FIG. 1 , the semiconductor device of the present invention comprises a substrate 100 , a gate structure 102 , a spacer 104 , a Si x Ge y layer 106 and a Si x Ge y protection layer 108 . The substrate 100 may be a silicon substrate or other appropriate semiconductor substrate. The gate structure 102 is deposited on the substrate 100 , and the gate structure 102 may be comprised of a gate dielectric layer (not shown) and a gate conductive layer (not shown). The material and forming method thereof are well known to one of the ordinary skill in the art, thus its detail is omitted herein. The spacer 104 is deposited on the sidewalls of the gate structure 102 . Moreover, the spacer 104 may be a single-layer spacer structure or a multi-layer spacer structure. The multi-layer spacer structure is composed of at least one offset spacer and one spacer.

In addition, the Si x Ge y layer 106 is deposited in the substrate 100 on both sides of the spacer 104 , and the Si x Ge y layer 106 is extended to a portion beneath part of the spacer 104 . The top level of the Si x Ge y layer 106 is higher than the surface of the substrate 100 . Wherein, the content of silicon-germanium in the Si x Ge y layer 106 is represented by Si x Ge y , and x+y<1. Moreover, it is to be noted that the so-called raised source/drain is formed by the Si x Ge y layer 106 , which provides a lower resistance and reduces the leakage current. However, the Si x Ge y layer 106 may cause the film being lost or damaged in the subsequent fabricating process. As a result, the reliability of the fabricating process and the device performance are affected.

Accordingly, in order to resolve the problem mentioned above, the semiconductor device of the present invention deposits a Si x Ge y protection layer 108 on the Si x Ge y layer 106 . To be more specific, the Si x Ge y protection layer 108 can prevent the underneath Si x Ge y layer 106 from being eroded by the cleaning agent during the subsequent cleaning process. In addition, the content of silicon-germanium in the Si x Ge y protection layer 108 is represented by Si x1 Ge y1 , where x1+y1<1 and 0≦y1<y. In more detail, the content of Ge (germanium) in the Si x Ge y protection layer 108 is lower than the content of Ge (germanium) in the Si x Ge y layer 106 , which lowers down the etch rate of the subsequent cleaning process and also prevents the underneath Si x Ge y layer 106 from being eroded, such that the Si x Ge y layer 106 is properly protected.

Referring to FIG. 2 , the semiconductor device according to an embodiment of the present invention further comprises a metal silicide layer 109 . The metal silicide layer 109 is deposited in part of the Si x Ge y protection layer 108 and on the gate structure 102 . The material of the metal silicide layer 109 is a refractory metal silicide, for example, wherein the refractory metal is selected from a group consisting of Ti (titanium), W (tungsten), Pt (platinum), Co (cobalt) and Ni (nickel). In addition, the metal silicide layer 109 is formed from the interaction with the silicon atoms in the Si x Ge y protection layer 108 beneath it, and at least half of the Si x Ge y protection layer 108 is used up. Thus, the thickness ratio (d1/d2) of the metal silicide layer 109 and the Si x Ge y protection layer 108 is between 0.5˜1.0. It is to be noted that the Si x Ge y protection layer 108 of the semiconductor device may be used for forming the metal silicide layer 109 , which protects the Si x Ge y layer 106 from being worn down.

FIG. 3 schematically shows a cross-sectional view of a semiconductor device according to a third embodiment of the present invention. Referring to FIG. 3 , the semiconductor device of the present invention comprises a substrate 100 , a gate structure 102 , a spacer 104 , a Si x Ge y B z layer 106 a and a Si x Ge y B z protection layer 108 a . The substrate 100 , the gate structure 102 , and the spacer 104 are the same devices described in the previous embodiment, thus they are indicated by the same number and the details are omitted herein. Moreover, the Si x Ge y B z layer 106 a is deposited in the substrate 100 on both sides of the spacer 104 and the Si x Ge y B z layer 106 a is extended to a portion beneath part of the spacer 104 . The top level of the Si x Ge y B z layer 106 a is higher than the surface of the substrate 100 . The material of the Si x Ge y B z layer 106 a is represented by Si x Ge y B z , and x+y+z<1. Furthermore, the concentration of boron (B) in the Si x Ge y B z layer 106 a is between 5×10 19 ×5×10 20 atoms/cm 3 .

In addition, the Si x Ge y B z protection layer 108 a is deposited on the Si x Ge y B z layer 106 a and the material of the Si x Ge y B z protection layer 108 a is represented by Si x Ge y B z , where x1+y1+z1<1 and 0<y1<y. Similarly, the Si x Ge y B z protection layer 108 a can prevent the film of the underneath Si x Ge y B z layer 106 a from being worn down or damaged during the subsequent fabricating process. Moreover, the content of Ge (germanium) in the Si x Ge y B z protection layer 108 a is lower than the content of Ge (germanium) in the Si x Ge y B z layer 106 a that the etch rate of the subsequent cleaning process is slowed down and the underneath Si x Ge y B z layer 106 a is prevented from being eroded.

Referring to FIG. 4 , the semiconductor device according to a fourth embodiment of the present invention further comprises a metal silicide layer 109 a . Wherein, the metal silicide layer 109 a is deposited in part of the Si x Ge y B z protection layer 108 a and on the gate structure 102 . The material of the metal silicide layer 109 is a refractory metal silicide, for example, wherein the refractory metal is selected from a group consisting of Ti (titanium), W (tungsten), Pt (platinum), Co (cobalt), and Ni (nickel). In addition, the thickness ratio (d3/d4) of the metal silicide layer 109 and the Si x Ge y B z protection layer 108 a is between 0.5˜1.0. Similarly, it is to be noted that the Si x Ge y B z protection layer 108 a of the semiconductor device may be used for forming the metal silicide layer 109 , which protects the Si x Ge y layer 106 from being worn down.

Of course, although the source/drain of the semiconductor device in the present invention is mainly made of silicon and germanium, it may be made by boron (B) or other atoms and should not be limited by Si x Ge y or Si x Ge y B z .

In summary, the present invention at least has the following advantages:

1. The semiconductor device of the present invention has a Si x Ge y protection layer or a Si x Ge y B z protection layer, which can prevent the film of the Si x Ge y layer or the Si x Ge y B z layer from being worn down or damaged during the subsequent fabricating process; and the reliability of the fabricating process and the device performance are not affected.

2. The content of Ge (germanium) in the Si x Ge y protection layer or the Si x Ge y B z protection layer is lower than the content of Ge (germanium) in the Si x Ge y layer or the Si x Ge y B z layer, which slows down the etch rate of the subsequent cleaning process and prevents the underneath Si x Ge y layer or the Si x Ge y B z layer from being eroded, such that the Si x Ge y layer or the Si x Ge y B z layer is properly protected.

3. In the semiconductor device of the present invention, the metal silicide layer may be formed by the Si x Ge y layer or the Si x Ge y B z layer, thus the Si x Ge y layer or the Si x Ge y B z layer will not be worn down.

Although the invention has been described with reference to a particular embodiment thereof, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed description.