In Ulsi Not Volatile Memory Technology And Product Reliability Test Research

From 1960s,NVM(Non-volatile Memory),as one of the two branches of Memory,has been developed quickly.There are many generations such as the MaskROM,UV erasable EPROM(Electrical Programming ROM),EEPROM (Electrical Erasable and Programming ROM),Flash and others;and most of them are also active in the marketing and play the roles in the commodity of digital products, like the game card,transportation card,smart card,U disk...Reliability is a scientific subject to study and analyses the product's lifetime in the normal used condition.Being an important property of the quality of a product, it's receiving more and more emphases now;the product with bad reliability performance must be washed out in the marketing since nobody would like to use it. So the design person has like to consider the potential reliability risk during the product design and layout to avoid the revenue loss in the future marketing.Integrated Circuits are always developing towards higher package density,larger storage capacity,faster operating speed.With the use of advanced technology and the shrinking of feature size,the inner electric field is also increased.It leads to larger leagage current and causes big challenge to semiconductor products.With the lapse of using time of products,those problems as MOS devices degradation,threshold drift, oxidation breakdown,decreasing of transconductance and interconnection fatigue will cause chip failure completely.Generally 10 years even 20 years lifetime for semiconductor products are requested.In order to make the reliability of lifetime be quantified,we introduced measurement method of acceleration lifetime whose characteristics is to get the sample's TTF(Time-To-Failure) under higher stress condition(including the Temperature,Voltage,Current,Pressure,Humidity...) to predict the lifetime under certain failure model at normal used condition,the prerequisite is the failure mechanism must be the same for them.The article is aiming at study the working feature of NVM products;study the typical test items,flows,and the criterion in process reliability part.For the hot carrier injection induced damage,we demonstrated and realized the improvement from decreasing the LDD dosage to lower the channel electrical filed.Regarding the endurance test in product reliability,the tunnel oxide and buried implant overlay issue induced CP soft failure and post reliability failure are illustrated;the relevant model and analysis are also presented.For data retention test in NVM product,no universal test pattern is suitable for all the failure mechanism.CKBD pattern is more sensitve than typical all 0 or all 1 when the floating gate to floating gate leakage is occurred between the neighbor bits.Also,we proposed the CP1,bake,and then CP2 flow for the NVM products shipment to minimize the early failure rate at the customer sit.