HSPICE-VCO simulation using BSIM level 54 model

[npn]

Hi,

I'm trying to simulate a ring oscillator based VCO in HSPICE. This is the netlist:

* VCO circuit

* **** MOS models *****
.MODEL n1 NMOS LEVEL=3
.MODEL p1 PMOS LEVEL=3
.GLOBAL VDD GND VIN

* ***** Define power supplies and sources *****
VDD VDD 0 2.2
VIN VIN 0 pwl 0 0 50n 0.2
VGND GND 0 0

* Subckt definitions
.subckt VCO_stage in n_in out p_in
M1 out in net1 GND n1 L=120n W=280n
M2 out in net2 VDD p1 L=120n W=980n
M3 net1 n_in GND GND n1 L=120n W=320n
M4 net2 p_in VDD VDD p1 L=120n W=1110n
.ends VCO_stage

* ***** Actual circuit topology *****
X1 a11 VIN a1 node1 VCO_stage
X2 a1 VIN a2 node1 VCO_stage
X3 a2 VIN a3 node1 VCO_stage
X4 a3 VIN a4 node1 VCO_stage
X5 a4 VIN a5 node1 VCO_stage
X6 a5 VIN a6 node1 VCO_stage
X7 a6 VIN a7 node1 VCO_stage
X8 a7 VIN a8 node1 VCO_stage
X9 a8 VIN a9 node1 VCO_stage
X10 a9 VIN a10 node1 VCO_stage
X11 a10 VIN a11 node1 VCO_stage


M5 node1 node1 VDD VDD p1 L=120n W=1110n
M6 node1 VIN GND GND n1 L=120n W=320n

* ***** Analysis statement *****
.TRAN 1n 50n

* ***** Output control statements *****
.OPTION POST PROBE
.PROBE V(VIN) V(a11)
.END


The simulation comes out fine when I use the level 3 model, but the level 54 model (which I want to use) doesn't seem to work.
Any idea why this is happening? Are there some basic guidelines about the models that I should know?

This is the circuit schematic. Ignore the laser target and the buffer.