METHOD FOR FABRICATING METAL-OXIDE SEMICONDUCTOR TRANSISTORS

Abstract

A method for fabricating a metal-oxide semiconductor transistor is disclosed. First, a semiconductor substrate having a gate structure thereon is provided, and a spacer is formed around the gate structure. An ion implantation process is performed to implant a molecular cluster containing boron into the semiconductor substrate surrounding the spacer for forming a source/drain region. The weight ratio of each boron atom within the molecular cluster is preferably less than 10%. Thereafter, a millisecond annealing process is performed to activate the molecular cluster within the source/drain region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 illustrate a method of utilizing pre-amorphorized implantation process for fabricating a p-type metal-oxide semiconductor (PMOS) transistor having ultra-shallow junction according to the prior art.

FIGS. 4-6 illustrate a method for fabricating a PMOS transistor according to the preferred embodiment of the present invention.

FIG. 7 illustrates the relative junction depth and dopant concentration measured while using dopants of different molecular weight and different fabrication parameters for fabricating ultra-shallow junctions according to the present invention.

FIG. 8 illustrates the relative resistance and junction depth measured while using either rapid thermal annealing process or laser annealing process for implanting B₁₈H₂₂ into a substrate.

Claims

1. A method for fabricating a metal-oxide semiconductor transistor, comprising: providing a semiconductor substrate;forming a gate structure on the semiconductor substrate;forming a spacer around the gate structure;performing a first ion implantation process to implant a molecular cluster having boron into the semiconductor substrate surrounding the spacer for forming a source/drain region, wherein the weight ratio of each boron atom within the molecular cluster is less than 10%; andperforming a millisecond annealing process for activating the molecular cluster within the source/drain region.

2. The method for fabricating a metal-oxide semiconductor transistor of claim 1, wherein the molecular cluster comprises BxHy and CxByHz.

3. The method for fabricating a metal-oxide semiconductor transistor of claim 2, wherein BxHy comprises B10H14 or B18H22.

4. The method for fabricating a metal-oxide semiconductor transistor of claim 1, wherein the molecular weight of the molecular cluster is greater than 100.

5. The method for fabricating a metal-oxide semiconductor transistor of claim 1 further comprising performing a second ion implantation process before forming the spacer to implant a molecular cluster having boron into the semiconductor substrate surrounding the gate structure for forming a lightly doped drain, wherein the weight ratio of each boron atom within the molecular cluster is less than 10%.

6. The method for fabricating a metal-oxide semiconductor transistor of claim 5, wherein the molecular cluster comprises BxHy and CxByHz.

7. The method for fabricating a metal-oxide semiconductor transistor of claim 6, wherein BxHy comprises B10H14 or B18H22.

8. The method for fabricating a metal-oxide semiconductor transistor of claim 5, wherein the molecular weight of the molecular cluster is greater than 100.

9. The method for fabricating a metal-oxide semiconductor transistor of claim 1, wherein the millisecond annealing process comprises a laser annealing process or a flash annealing process.

10. The method for fabricating a metal-oxide semiconductor transistor of claim 1, wherein the duration of the millisecond annealing process is between 100 milliseconds to 1 microsecond.

11. The method for fabricating a metal-oxide semiconductor transistor of claim 1, wherein the temperature of the millisecond annealing process is between 1100 degrees to 1500 degrees.

12. A metal-oxide semiconductor transistor, comprising: a semiconductor substrate;a gate structure disposed on the semiconductor substrate;a spacer formed around the gate structure; anda source/drain region formed in the semiconductor substrate, wherein the source/drain region comprises at least one molecular cluster having boron therein, wherein weight ratio of each boron atom within the molecular cluster is less than 10%.

13. The metal-oxide semiconductor transistor of claim 12, wherein the molecular cluster comprises BxHy and CxByHz.

14. The metal-oxide semiconductor transistor of claim 13, wherein BxHy comprises B10H14 or B18H22.

15. The metal-oxide semiconductor transistor of claim 12, wherein the molecular weight of the molecular cluster is greater than 100.

16. The metal-oxide semiconductor transistor of claim 12 further comprising a lightly doped drain formed in the semiconductor substrate surrounding the gate structure, wherein the lightly doped drain comprises at least one molecular cluster having boron therein, wherein the weight ratio of each boron atom within the molecular cluster is less than 10%.

17. The metal-oxide semiconductor transistor of claim 16, wherein the molecular cluster comprises BxHy and CxByHz.

18. The metal-oxide semiconductor transistor of claim 17, wherein BxHy comprises B10H14 or B18H22.

19. The metal-oxide semiconductor transistor of claim 16, wherein the molecular weight of the molecular cluster is greater than 100.