Squeaks and other sounds typically begin to develop when there is insufficient lubrication on the door hinge. The action of opening and closing the door slowly causes the product applied at the factory to thin out. Consequentially, noisy hinges are usually associated with older appliances.
Worn or loose hinge parts generate noise and make the doors harder to open. Damage usually occurs when there has been insufficient lubrication on the moving parts of the hinge for a prolonged period. Well-maintained doors silently swing closed when released from a 45-degree angle.
Disassemble the problem hinge while supporting the weight of the door, and apply a silicon-based or petroleum jelly lubricant. In a pinch, apply vegetable or canola oil to the metal shaft. Put the door back together and open the refrigerator a few times to work the lubricant into the hinge. WD-40 and other moisture-dispersing sprays provide short-term lubrication.
Worn washers and loose screws could be causing the noise; remove the hinge screws at the top of the refrigerator while an assistant supports the weight of the door. Pull the hinge plate off the top of the refrigerator, and lift the door off the lower hinge. Inspect for signs of worn washers or other parts, and purchase replacements if necessary.