Data Retention Performance of 0.13µm Ramtron F-RAM Memory

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1 Data Retention Performance of 0.13µm Ramtron F-RAM Memory Shan Sun, Ph. D. and Scott Emley Overview This document confirms the data retention specifications of AEC-Q100 Grade 3, Grade 2, and Grade 1 (0.13µm) F-RAM Memory Products from Ramtron. If operated within product specification and with 2T2C cell structure, F-RAM has theoretically unlimited Same State (SS) data retention, while Opposite State (OS) data retention of F-RAM is limited. The OS retention time prediction of Ramtron s 0.13µm F-RAM Memory Products is based on reliability test results after extended bakes and the activation energy (Ea) of 1.4 ev provided by the manufacturer. This paper provides a method to calculate the OS data retention life times for customized temperature profiles. F-RAM Retention Lifetime A primary reliability measured quantity of F-RAM is the retention lifetime of a capacitor cell that has been previously stored in a polarization state for an extended time and then written to the opposite polarization state. This type of retention is known as Opposite State (OS) retention due to imprint. Imprint makes the previously stored state, or so-called Same State (SS), more stable over stored time. Therefore, F-RAM has an unlimited SS date retention within the specified temperature range. This white paper focuses on OS retention performance. OS Retention is often specified as an amount of time at a given constant temperature. Thus, this paper discloses the OS retention (time) specification of AEC-Q100 Grade 3, 2, and 1 products from Ramtron for constant temperature profiles, but concludes with a cumulative scenario including multiple temperature profiles over the life of the product. 1 Copyright 2012 Ramtron International Corp.

If operated within product specification and with 2T2C cell structure, F-RAM has theoretically unlimited Same State (SS) data retention, while Opposite State (OS) data retention of F-RAM is limited.

2 AEC-Q100 Grade 3 Ramtron F-RAM OS Retention Based on accelerated and extended stress experimental results and Ea of 1.4 ev, 10 years of OS retention at 85 o C is guaranteed. The OS retention times at various temperatures are calculated, as shown in Figure 1. The OS retention increases exponentially as temperature decreases. For example, it is 36.8 years at 75 o C and >100 years at 65 o C. Below 65 o C, the OS retention is virtually unlimited. AEC-Q100 Grade 2 Ramtron F-RAM OS Retention Based on accelerated and extended stress experimental results and Ea of 1.4 ev, 5 years or 43.8k hours of OS retention at 105 o C is guaranteed. The OS retention times at various temperatures are calculated, as shown in Figure 2. This specification can be converted to more common temperatures. For example, it is equivalent to 43k hours at 105 o C plus 64 years at 55 o C. The life time prediction for specific application temperature profiles will be discussed in a later section. 2 Copyright 2012 Ramtron International Corp.

8 years at 75 o C and >100 years at 65 o C. Below 65 o C, the OS retention is virtually unlimited.

3 OS Data Retention (years) 1e+14 1e+13 1e+12 1e+11 1e+10 1e+9 1e+8 1e+7 1e+6 1e+5 1e+4 1e+3 1e+2 1e+1 1e Application Temperature ( o C) Figure 1. OS retention time of Grade 3 F-RAM at various temperatures. OS Data Retention (years) 1e+14 1e+13 1e+12 1e+11 1e+10 1e+9 1e+8 1e+7 1e+6 1e+5 1e+4 1e+3 1e+2 1e+1 1e Application Temperature ( o C) Figure 2. OS retention time of Grade 2 F-RAM at various temperatures. 3 Copyright 2012 Ramtron International Corp.

100 120 Application Temperature ( o C) Figure 2. OS retention time of Grade 2 F-RAM at various temperatures.

4 AEC-Q100 Grade 1 Ramtron F-RAM OS Retention The most recent accelerated and extended stress experimental results suggest that the OS retention time of Ramtron s Grade 1 F-RAM products is >11,163 hours at 125 o C. This result supports the specification of 11,000 hours at 125 o C. The specified OS retention times at various temperatures within the specified temperature range (-45 o C to 125 o C) are calculated, as shown in Figure 3. The specification can be converted to other temperature profiles. The life time predication of specific application temperature profiles is illustrated in the next section. OS Data Retention (years) 1e+14 1e+13 1e+12 1e+11 1e+10 1e+9 1e+8 1e+7 1e+6 1e+5 1e+4 1e+3 1e+2 1e+1 1e+0 1e Application Temperature ( o C) Figure 3. OS retention time of Grade 1 F-RAM at various temperatures. 4 Copyright 2012 Ramtron International Corp.

The specified OS retention times at various temperatures within the specified temperature range (-45 o C to 125 o C) are calculated, as shown in Figure 3.

5 OS Retention Life Predication for Customized Temperature Profiles Most of the previous sections focused on the OS data retention specification of AEC-Q100 Grade 1, Grade 2, or Grade 3 F-RAM at a fixed temperature. However, it is rare for an application to actually operate under a steady temperature for the entire usage life time of the application. Instead, an application is often expected to operate in multiple temperature environments throughout the application s usage life time. Accordingly, the retention specification for F-RAM in applications often needs to be calculated cumulatively. For example: Assuming one customer uses Ramtron s Grade 1 F-RAM for an application that requires the temperature profile over the following usage life time: Temperature 1 = 125 o C with 10% of time (t1) Temperature 2 = 105 o C with 15% of time (t2) Temperature 3 = 85 o C with 25% of time (t3) Temperature 4 = 55 o C with 50% of time (t4) Following the Arrhenius relation, the acceleration factor A of Tmax to T is: Ea 1 ( ( T ) k T T L A = = e L( T max) 1 max ) Where k is the Boltzmann constant 8.617x10-5 ev/k, Tmax is the highest temperature specified by Ramtron for the product, and T is any temperature within Ramtron s specification. All temperatures are in Kelvin. The acceleration factors are listed in Table 1. Table 1 (1) Temperature Time Factor Acceleration Factor Tmax Profile Factor Profile Life time (T) (t) (A) (P) L(P) T1=125 o C 0.1 A1=1 1 P = L(P)=P*L(Tmax) T2=105 o t1 t2 t3 t4 C 0.15 A2= A1 A2 A3 A4 T3=85 o C 0.25 A3=95.68 =10.46 years T3=55 o C 0.5 A3= = 8.33 The Profile factor P is determined by: P = t1 + A1 1 t2 + A2 t3 + A3 t4 A4 (2) 5 Copyright 2012 Ramtron International Corp.

Instead, an application is often expected to operate in multiple temperature environments throughout the application s usage life time.

6 The OS retention life time prediction of a temperature profile, L(P), is given by: L ( P) = P * L( T max) (3) Where L(Tmax) is the specified OS retention time 11,000 hours at 125 o C. The calculation process and results are listed in Table 1. It is seen that the life time of a profile is dominated by the highest usage temperature and its time factor. Note that in the calculation, T is equal to or lower than Tmax. It is mathematically correct to use Equations when T > Tmax, and T < Tmin, however Ramtron does not guaranty the parts working properly when T is out of the temperature specifications. Summary Table 2 summarizes the Tmax, the OS retention life time specification at Tmax i.e., L(Tmax), and OS retention life time calculation of a general temperature profile. F-Ram Product Tmax OS retention at Tmax OS Retention Life Time Of Temperature Profile Determined by customers Grade o C 11k hours Grade o C 5 years Grade 3 85 o C 10 years 1 P =, L( P) = P * L( T max) t A For more information You can find out more about how F-RAM semiconductor products can improve your next system design via the following resources: For general information, visit To order a product sample, visit To contact your local authorized sales representative, visit Call Customer Service at , or info@ramtron.com 6 Copyright 2012 Ramtron International Corp.

Note that in the calculation, T is equal to or lower than Tmax.

7 About Ramtron International Corporation Ramtron International Corporation, headquartered in Colorado Springs, Colorado, is a fabless semiconductor company that designs, develops, and markets specialized semiconductor memory and integrated semiconductor solutions used in a wide range of product applications and markets worldwide. For more information, visit Ramtron International Corporation, 1850 Ramtron Drive, Colorado Springs, CO Copyright 2012 Ramtron International Corp.

semiconductor solutions used in a wide range of product applications and markets worldwide. For more information, visit www.

Preliminary Evaluation of Data Retention Characteristics for Ferroelectric Random Access Memories (FRAMs).

1 Preliminary Evaluation of Data Retention Characteristics for Ferroelectric Random Access Memories (FRAMs). 1.0 Introduction 1.1 FRAM Technology Background Ashok K. Sharma/NASA Ashok.k.Sharma.1@gsfc.nasa.gov