US-12618893-B2 - Apparatus and method of measuring reliability for flash memory material through a current measurement

US12618893B2US 12618893 B2US12618893 B2US 12618893B2US-12618893-B2

Abstract

A reliability measuring apparatus includes an oxide-nitride-oxide-alumina (ONOA) current measuring circuit configured to measure an ONOA current by applying an ONOA current measuring voltage to a selected word line coupled to a selected memory cell in a flash memory and a reliability indicator generator configured to a reliability indicator using the ONOA current measured through the measuring circuit.

Inventors

Nam Cheol JEON
Hea Jong Yang
Tae Un Youn

Assignees

SK Hynix Inc.

Dates

Publication Date: 20260505
Application Date: 20231102
Priority Date: 20221111

Claims (15)

1 . A flash memory material reliability measuring apparatus using current measurement comprising: an oxide-nitride-oxide-alumina (ONOA) current measuring circuit configured to measure an ONOA current by applying a ONOA current measuring voltage to a selected word line coupled to a selected memory cell in a flash memory; and a reliability indicator generator configured to generate a reliability indicator using the ONOA current measured through the ONOA current measuring circuit, wherein the reliability indicator generated in the reliability indicator generator includes at least one of an endurance indicator, a retention indicator, a disturbance indicator, an interference indicator, and a tunnel oxide (TOX) nitrogen gradient indicator of the flash memory.
2 . The apparatus of claim 1 , wherein the ONOA current measuring circuit selects a memory cell string including the selected memory cell, as an ONOA current measuring target, from a memory cell array of the flash memory, applies a zero (0) voltage to a selected bit line and a selected source line coupled to the selected memory cell, applies a pass voltage to unselected word lines, applies an ONOA current measuring voltage to a selected word line coupled to the selected memory cell, and measures the ONOA current.
3 . The apparatus of claim 1 , wherein the ONOA current measuring circuit applies the ONOA current measuring voltage applied to the selected word line coupled to the selected memory cell through a plurality of sweep processes, one of the plurality of sweep processes includes a sweep period in which the ONOA current measurement voltage is applied for a fixed time to rise to the Fowler-Nordheim (FN) tunneling threshold voltage, and a maintenance period in which the ONOA current measurement voltage is maintained at for a fixed time after the sweep period.
4 . The apparatus of claim 3 , wherein the ONOA current measuring circuit measures the ONOA current during the sweep period.
5 . The apparatus of claim 4 , wherein the ONOA current measuring circuit measures the ONOA current during a sweep period included in one sweep process selected from among the sweep processes excluding the first sweep process among the plurality of sweep processes.
6 . The apparatus of claim 3 , wherein the ONOA current measuring circuit applies a pass voltage to the unselected word line during the sweep period and applies 0V to the unselected word line during the maintenance period.
7 . The apparatus of claim 1 , further comprising a material managing circuit configured to apply the reliability indicator generated in the reliability indicator generator to a material of the flash memory, perform screening on the material to exclude the material of the flash memory or grading on the material to assign a grade to the material, and output a material management result according to the screening or grading.
8 . A method of measuring reliability of a material of a flash memory using a flash memory material reliability measuring apparatus, which includes an Oxide-Nitride-Oxide-Alumina (ONOA) current measuring circuit, a reliability indicator generator, and a material managing circuit, the method comprising: the ONOA current measuring circuit measuring an ONOA current via a tunnel insulating layer through Fowler-Nordheim (FN) tunneling by applying an ONOA current measuring voltage to a selected word line coupled to a selected memory cell of the flash memory; and the reliability indicator generator generating a reliability indicator using the ONOA current measured in the ONOA current measuring circuit, wherein the reliability indicator generated in the reliability indicator generator includes at least one of an endurance indicator, a retention indicator, a disturbance indicator, an interference indicator, and a tunnel oxide (TOX) nitrogen gradient indicator of the flash memory.
9 . The method of claim 8 , wherein the measuring of the ONOA current includes: by the ONOA current measuring circuit, selecting a memory cell string including the selected memory cell, as an ONOA current measuring target, from a plurality of cell strings in a memory cell array of the flash memory; applying a zero (0) voltage to a selected bit line and a selected source line coupled to the selected memory cell; applying a pass voltage to unselected word lines; applying the ONOA current measuring voltage to the selected word line; and measuring the ONOA current.
10 . The method of claim 8 , wherein in the measuring of the ONOA current includes applying an ONOA current measuring voltage to a selected word line coupled to the selected memory cell through a plurality of sweep processes, wherein the plurality of sweep processes perform one sweep process multiple times, wherein the one sweep process includes a sweep period in which the ONOA current measurement voltage is applied for a fixed time to rise to the Fowler-Nordheim (FN) tunneling threshold voltage, and a maintenance period in which the ONOA current measurement voltage is maintained at 0V for a fixed time after the sweep period.
11 . The method of claim 8 , wherein the ONOA current measuring circuit measuring the ONOA current measures the ONOA current during a sweep period.
12 . The method of claim 11 , wherein ONOA current measuring circuit the measuring the ONOA current measures the ONOA current during the sweep period included in one sweep process selected from among sweep processes excluding the first sweep process among the plurality of sweep processes.
13 . The method of claim 10 , wherein the measuring of the ONOA current applies a pass voltage to the unselected word line during the sweep period and applies 0V to the unselected word line during the maintenance period.
14 . The method of claim 8 , further comprising managing, by the material managing circuit, applying the reliability indicator generated in the reliability indicator generator to a material of the flash memory, performing management on the material by screening on the material to exclude the material or by grading on the material to assign a grade for the material, and outputting a material management result according to the screening or grading.
15 . A readable recording medium in which codes, which are read by a computer to execute the material reliability measuring method of claim 8 , are recorded.

Description

CROSS-REFERENCES TO RELATED APPLICATION The present application claims priority under 35 U.S.C. § 119(a) to Korean Patent Application Number 10-2022-0150415, filed on Nov. 11, 2022, in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety. BACKGROUND 1. Technical Field Various embodiments may generally relate to a reliability measuring technology for a flash memory, and more particularly, to an apparatus and method of measuring reliability for a flash memory material capable of predicting reliability characteristics of a flash memory material by measuring current flowing via a tunneling insulator and performing material management during a flash memory manufacturing process. 2. Related Art In general, semiconductor memory apparatuses exhibit a bathtub curve characteristic including an early failure period, an intrinsic failure period and a wear-out failure period. The early failure period refers to a period that many unexpected defects occur. The intrinsic failure period refers to a period that random defects of a semiconductor itself occur after the early failure period. The wear-out failure period refers to a period that an intrinsic wear mechanism starts and a failure rate increases exponentially. Accordingly, a semiconductor reliability evaluation which measures reliability indicators to ensure reliability is performed in a semiconductor manufacturing process. The typical examples of the reliability indictors are electromigration (EM) which characterizes the quality of metals with high current and temperature, hot carrier injection (HCI) that carriers of a channel region of a device receive high energy and inject into an insulating layer to change a threshold voltage VT of the device, time dependent dielectric breakdown (TDDB) that the carries injected into the insulating layer short-circuit a substrate and a gate of the device, bias temperature instability (BTI) that a threshold voltage VT of a device is shifted when 0, 1, 0, 1 . . . are successively repeated, endurance, retention, disturbance, interference, and a tunneling oxide (TOX) nitrogen gradient of a memory cell, and the like. However, there is a limit in that the reliability-related items such as the endurance, retention, disturbance, interference, or the TOX nitrogen gradient can be measured only in very few materials during the semiconductor mass production process due to limitations of a measuring time and equipment. SUMMARY In an embodiment of the present disclosure, a flash memory material reliability measuring apparatus through current measurement may include: an oxide-nitride-oxide-alumina (ONOA) current measuring circuit configured to measure an ONOA current by applying an ONOA current measuring voltage to a selected word line coupled to a selected memory cell in a flash memory; and a reliability indicator generator configured to generate a reliability indicator using the ONOA current measured through the ONOA current measuring circuit. In an embodiment of the present disclosure, a method of measuring reliability of a material of a flash memory using a flash memory material reliability measuring apparatus, which includes an Oxide-Nitride-Oxide-Alumina (ONOA) current measuring circuit, a reliability indicator generator, and a material managing circuit, the method may include: the ONOA current measuring circuit measuring an ONOA current via a tunnel insulating layer through Fowler-Nordheim (FN) tunneling by applying an ONOA current measuring voltage to a selected word line coupled to a selected memory cell of the flash memory; and the reliability indicator generator generating a reliability indicator using the ONOA current measured in the ONOA current measuring circuit. BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects, features and advantages of the subject matter of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a circuit diagram illustrating a memory cell array constituting a flash memory to explain a flash memory material reliability measuring apparatus through current measurement according to an embodiment of the present disclosure; FIG. 2 is a functional block diagram illustrating a flash memory material reliability measuring apparatus through current measurement according to an embodiment of the present disclosure; FIG. 3 is a functional block diagram illustrating an ONOA current measuring circuit in a flash memory material reliability measuring apparatus through current measurement according to an embodiment of the present disclosure; FIG. 4 is a graph illustrating an ONOA current measuring voltage (positive (+) bias) applied to a word line by a word line controller in a flash memory material reliability measuring apparatus through current measurement according to an embodiment of the present disclosure; FIG. 5 is a diagram illustrating an energy band dia