Interconnection patterns in integrated circuits are made on the metal layer. This layer is typically made of aluminum or copper and is used to connect different components, such as transistors and resistors, on the chip.

The interconnection pattern plays a crucial role in the functioning of an integrated circuit. It determines the paths through which electrical signals flow, enabling communication between different parts of the circuit. The interconnections are designed to minimize signal delay, power consumption, and electromagnetic interference.

Here is a detailed explanation of why the correct answer is option 'C' - metal layer:

1. Purpose of interconnections:
- Interconnections are used to establish electrical connections between various components on the chip.
- They provide paths for the flow of electrical signals, enabling communication and data transfer between different parts of the circuit.

2. Material used for interconnections:
- The metal layer is chosen for interconnections due to its excellent electrical conductivity.
- Aluminum and copper are commonly used metals as they have low resistivity, allowing for efficient signal transmission.

3. Location of the metal layer:
- The metal layer is typically located above the semiconductor material, such as silicon.
- It is placed on top of the various layers of the integrated circuit, including the polysilicon layer, silicon-di-oxide layer, and diffusion layer.

4. Advantages of using the metal layer:
- The metal layer provides a high level of flexibility in designing the interconnection pattern.
- It allows for the creation of complex interconnection patterns, enabling efficient routing of signals.
- The metal layer can be easily patterned using techniques such as photolithography, making it suitable for mass production of integrated circuits.

In conclusion, the interconnection pattern in integrated circuits is made on the metal layer. This layer, typically made of aluminum or copper, provides an efficient and flexible means of connecting various components on the chip. It allows for the creation of complex interconnection patterns, enabling efficient signal transmission and communication within the circuit.