# Fabrication and Testing of Thermoelectric CMOS-MEMS Microgenerators with CNCs Film
## 1 Introduction  
A rapidly growing population results in the consumption of a large amount of energy. Nowadays, fossil fuels are the main energy source in the world. Unfortunately, fossil fuels increase exhausts, which cause air pollution and the greenhouse effect. After most of the energy is used, it is transformed into waste heat, and then dissipated ambiently. If waste heat can be converted to electrical power, it will provide more energy and reduce carbon emissions.  
Micro-electro-mechanical-system (MEMS) techniques have been applied in the manufacturing of microactuators and microdevices [1; 2; 3; 4; 5]. Recently, micro thermoelectric generators were developed using MEMS technology. For instance, [PERSON] et al. [6] manufactured TMG using micromachining and electroplating. Materials of thermopiles in the microgenerator were bismuth telluride and antimony telluride because they had a high thermoelectric coefficient. Bismuth telluride and antimony telluride that were n-type and p-type semiconductors, respectively, were deposited on a polymer substrate. Thereby, the microgenerator had a flexible property, and its power density was 9.2 mW/cm\({}^{2}\) at TD 52 K. [PERSON] [7] proposed planar TMG with an excellent thermal property. The structure of TMG contained polysilicon-based thermopiles and a membrane, which were fabricated by periodically etching siliconsubstrates. [PERSON] et al. [8] fabricated a TMG on a silicon substrate utilizing a CMOS process. The structure of the thermogenerator consisted of a single-crystalline silicon membrane that was 100 nm thick with n- and p-type doped thermopiles. This device had an OP density of 4.5 \(\upmu\)W/cm\({}^{2}\) at TD 5 K. [PERSON] [9] utilized micromachining to make the TMG. Thermopiles of the generator had a high aspect ratio structure. The microgenerator had an OV factor of 0.16 V/K/cm\({}^{2}\) and an OP factor of 9.3 \(\upmu\)W/K\({}^{2}\)/cm\({}^{2}\). [PERSON] et al. [10] manufactured a thermoelectric microgenerator on a glass substrate using a single Sb doped ZnO microwire. The microgenerator had a maximum OV of 68 mV at TD 20 K. [PERSON] [11] made flexible thin-film thermoelectric generators utilizing electroplating. Thermopiles were constructed by n-type bismuth telluride and p-type antimony telluride, which were deposited on a flexible substrate using electroplating, followed by a transfer process. The flexible TMG power was 10.4 nW under TD 60 K. [PERSON] [12] developed a silicon nanowire TMG. The thermoelectric generator was made on a silicon substrate utilizing micromachining, and the surface of the generator was covered with silicon dioxide layers.  
Many MEMS components manufactured utilizing CMOS technology are called CMOS-MEMS devices [13; 14; 15; 16]. Fabrication of these devices is compatible with the IC (integrated circuit) process, so that they are able to integrate with IC on a chip [17; 18; 19; 20; 21]. In this study, we make a COMS-MEMS thermoelectric microgenerator with a CNCs film. The microgenerator is a kind of CMOS-MEMS device, and it has potential for integration with IC for application in electronic devices and sensors. In order to enhance heat absorption at HP in thermopiles, CNCs are deposited on the surface in the microgenerator. The HP in the thermopiles is a suspension structure isolating heat dissipation, and the CP in thermopiles is anchored on the substrate increasing the heat sink, leading to enhancement of the TD in thermopiles.