TECHNICAL FIELD

This disclosure relates generally to deposition of a transition metal on a semiconductor substrate and, more particularly to deposition of a transition metal on a semiconductor substrate by conversion of a boron layer that is formed by a boron-containing precursor.

BACKGROUND

Deposition of tungsten and tungsten-containing materials is an integral part of many semiconductor fabrication processes. Such deposition may be accomplished via chemical vapor deposition (CVD) techniques, plasma-enhanced CVD (PECVD) techniques, atomic layer deposition (ALD) techniques, as well as other deposition techniques known in the IC fabrication arts such as, for example, physical vapor deposition (PVD). Tungsten and tungsten-containing materials, hereinafter referred to as tungsten-based materials or just tungsten materials, may be used for horizontal interconnects, vias between adjacent metal layers, contacts between first metal layers and devices on the silicon substrate, and may generally be used within various high aspect ratio features utilized in IC design.

In a conventional process for depositing tungsten material, a substrate is heated to a predetermined process temperature in a deposition chamber, and a thin layer of tungsten material is deposited to serve as a seed or nucleation layer. Thereafter, a bulk layer of tungsten material is deposited atop the nucleation layer. Conventionally, the tungsten material is formed by the reduction of tungsten hexafluoride (WF6) with hydrogen (H2). Typically, tungsten material is deposited over an entire exposed surface area of the substrate which often includes one or more field regions, as well as various IC features. These features may have widely varying aspect ratios, and in some embodiments, one or more or all features may have relatively high aspect ratios.

SUMMARY

This disclosure pertains to a method. The method includes providing a gas mixture in a gas supply line, where the gas mixture includes diborane (B2H6) with a balance of hydrogen (H2). The method further includes introducing the gas mixture from the gas supply line into a deposition chamber to a surface of a semiconductor substrate, where the semiconductor substrate includes a vertical structure having a plurality of horizontally-oriented features, where the diborane decomposes to form a boron layer in the horizontally-oriented features. The method further includes converting the boron layer to a transition metal layer in the semiconductor substrate.

In some implementations, the gas mixture includes at least 20% by volume of diborane with the balance of hydrogen. In some implementations, the gas mixture includes between about 20% and about 50% by volume of diborane with a balance of hydrogen. In some implementations, the transition metal includes molybdenum, ruthenium, cobalt, or tungsten. In some implementations, converting the boron layer to the transition metal layer includes reacting the boron layer with a tungsten-containing precursor to form a tungsten layer. In some implementations, the semiconductor substrate has openings in sidewalls of the vertical structure that are fluidically accessible from the vertical structure through the openings. In some implementations, the vertical structure is a three-dimensional (3-D) vertical NAND structure. In some implementations, the boron layer is conformally deposited in the horizontally-oriented features of the vertical structure, the boron layer having a step coverage of at least 90%.

This disclosure also pertains to an apparatus. The apparatus includes a gas supply line and a deposition chamber coupled to the gas supply line, where the deposition chamber is configured to process a semiconductor substrate in the deposition chamber, and where the gas supply line is configured to contain a gas mixture of diborane with a balance of hydrogen. The semiconductor substrate includes a vertical structure having a plurality of horizontally-oriented features. The apparatus further includes a controller configured to provide instructions for performing the following operations: introducing the gas mixture from the gas supply line into the deposition chamber to the surface of the semiconductor substrate, where the diborane decomposes to form a boron layer in the horizontally-oriented features, and converting the boron layer to a transition metal layer in the semiconductor substrate.

In some implementations, the gas mixture includes at least 20% by volume of diborane with the balance of hydrogen. In some implementations, the gas mixture includes between about 20% and about 50% by volume of diborane with the balance of hydrogen. In some implementations, the transition metal layer includes molybdenum, ruthenium, cobalt, or tungsten. In some implementations, the system controller configured with instructions for converting the boron layer is configured with instructions for reacting the boron layer with a transition metal precursor to form the transition metal layer. In some implementations, the semiconductor substrate has openings in sidewalls of the vertical structure that are fluidically accessible from the vertical structure through the openings. In some implementations, the controller is further configured with instructions for performing the following operation: exposing the semiconductor substrate to a reducing gas, wherein the reducing gas includes silane, disilane, or hydrogen. In some implementations, the controller is further configured with instructions for performing the following operation: providing the semiconductor substrate in the deposition chamber.

These and other embodiments are described further below with reference to the figures.

