Physically unclonable function device with a load circuit to generate bias to sense amplifier

#In the field of semiconductor manufacturing, even if there are two identical integrated circuits on the same die using the same manufacturing process and the same material, each integrated circuit would still be unique. This is due to the physical randomness introduced during the manufacturing steps. This inherent variation may be extracted and used as unique identifications and can be thought of as being similar to DNAs of human beings. Physically unclonable function have been proposed and have gained popularity recently as a cryptographic key generator. A PUF, based on its physical properties, may be evaluated easily and would produce an output, but such output could be hard to predict. This output may be used to provide a unique identity, since such variations are rarely the same. The unique identify cannot be easily to cloned as a direct copy of the same circuit when manufactured will produce a different signature (ID) from the original on being cloned. Many PUF circuits have been proposed. An important property of a PUF circuit is reliability. That is, a PUF circuit must be able to generate the same signature (ID) at all operating conditions and after it has been operated for a long time.

#Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

#FIG. 1 illustrates a schematic block diagram of a physically unclonable function (PUF) device according to an exemplary embodiment of the disclosure.

#FIG. 2 illustrates a schematic diagram of a PUF device according to an exemplary embodiment of the disclosure.

#The following disclosure provides many different embodiments, or examples, for implementing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

#Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

#A masking method may be employed to improve the reliability of PUF device as it operates under different operating conditions which may results in different signatures. Hence, we define a bit as stable when the bit stays in the same state under different operating conditions. A bit (generated by a PUF cell) is unstable, if the bit ends up in a different state under different conditions. Different operating conditions may be defined in terms of varying supply voltage or varying temperature for an example. The design masking method may identify a bit (from a PUF cell) to be unstable or stable during the masking phase. Once a mask is derived, the stable bit may be used in the actual generation of signature. After identification, the identified bits which are marked as stable may use as a final signature and bits which are marked as unstable are not used in a generation of signature. Identifying the unstable bits in the marking phase may achieved by adding all possible noises or stress to mimic the effect of the circuit behavior under different operating conditions in the PUF device. The mask stable bit is obtained by the PUF device which may tolerate the added noises under different operating conditions established during the marking phase. By adopting this method, an extra noise injection circuit may be needed however it is difficult and expensive to establish the different operating conditions during the marking phase. In addition, external power supply and external thermal condition system may be needed to establish the different operating conditions in the marking phase identify the stable and unstable bits to generate the PUF device with same signature ID.