Placement matters: One way to decide how good a decoupling capacitor placement is by looking at the discharge current loop. Continue from previous post (http://electroniccircuitdesignsharing.blogspot.com/2012/07/3d-current-flow-for-inverting-op-amp.html), re-placing the decoupling capacitor near IC pin6 to bottom and just under supply pin will allow much better decoupling performance due to smaller discharge current loop. Compare diagrams below with the ones shown in previous post for details.
Top view of top signals
Top view of bottom signals