JPH01116999A - Product inspecting method for eeprom - Google Patents
Product inspecting method for eepromInfo
- Publication number
- JPH01116999A JPH01116999A JP62274197A JP27419787A JPH01116999A JP H01116999 A JPH01116999 A JP H01116999A JP 62274197 A JP62274197 A JP 62274197A JP 27419787 A JP27419787 A JP 27419787A JP H01116999 A JPH01116999 A JP H01116999A
- Authority
- JP
- Japan
- Prior art keywords
- threshold voltage
- eeprom
- test
- dedicated area
- shift quantity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims description 5
- 238000012360 testing method Methods 0.000 claims abstract description 27
- 238000007689 inspection Methods 0.000 claims description 4
- 230000001133 acceleration Effects 0.000 abstract description 6
- 230000002950 deficient Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 230000005641 tunneling Effects 0.000 description 1
Landscapes
- For Increasing The Reliability Of Semiconductor Memories (AREA)
- Techniques For Improving Reliability Of Storages (AREA)
- Read Only Memory (AREA)
Abstract
Description
【発明の詳細な説明】 〈産業上の利用分野〉 本発明は、ＥＥＰＲＯＭの製品検査方法に関する。[Detailed description of the invention] <Industrial application field> The present invention relates to an EEPROM product inspection method.
〈従来の技術〉
近年、マイクロコンピュータの使用分野は多岐にわたっ
ているため、そのプログラム内容も多種多様であり、し
たがって、それぞれの用途に合わせて開発されたシステ
ムプログラムを書き込み、また、システム変更に対応し
てその内容を書き換えろことができるＲＯＭが必要とな
る。その要求に応えるものとして、ユーザがデータを電
気的に書き換えることができる、いわゆるＥＥＰＲＯＭ
（Ｅｌｅｃｔｒｉｃａｌｌｙ Ｅｒａｓａｂｌｅ ａｎ
ｄ Ｐｒｏｇｒａｍａｂｌｅ ＲＯＭ）がある。第３図
にＥＥＰＲＯＭの一例としてフローティングゲート型の
ものを示す。同図において、ｌはコントロールゲート、
２はフローティグゲート、３はトンネル領域、４はソー
ス、５はドレイン、６は基板である。そして、コントロ
ールゲートｌまたはソース４に高電圧を印加することに
より、各メモリセルのしきい値電圧■ が瞬時にデイプ
レッション側もしくはエンハンス側にシフトし、これに
よってデータの書き込みあるいは消去がなされる。<Conventional technology> In recent years, microcomputers have been used in a wide variety of fields, and their program contents are also diverse. A ROM whose contents can be rewritten is required. In order to meet this demand, so-called EEPROM, which allows users to electrically rewrite data, has been developed.
(Electrically Erasable an
d Programmable ROM). FIG. 3 shows a floating gate type EEPROM as an example. In the figure, l is a control gate,
2 is a floating gate, 3 is a tunnel region, 4 is a source, 5 is a drain, and 6 is a substrate. By applying a high voltage to the control gate 1 or the source 4, the threshold voltage 2 of each memory cell is instantaneously shifted to the depletion side or the enhancement side, thereby writing or erasing data.
このように、ＥＥＰＲＯＭのしきい値電圧Ｖは、高電圧
の印加によるトンネル現象によって電子あるいは正孔が
薄膜を通過することによって生じるため、第４図に示に
示すように、しきい値電圧Ｖ は時間経過とともに次第
に低下して定常状態に戻ろうとする傾向がある。そして
、しきい値電圧Ｖ が極度に低下した場合には、メモリ
セルに記憶していたデータが失われてしまう。また、し
きい値電圧Ｖ は、第４図の破線で示すようにシフト量
が小さいものや、実線で示すようにシフト量か大きいも
の等、製品ごとにばらつきがある。In this way, the threshold voltage V of an EEPROM is generated when electrons or holes pass through a thin film due to the tunneling phenomenon caused by the application of a high voltage. tends to gradually decrease and return to a steady state over time. Then, if the threshold voltage V 2 drops extremely, the data stored in the memory cell will be lost. Further, the threshold voltage V 1 varies from product to product, with some having a small shift amount as shown by the broken line in FIG. 4, and others having a large shift amount as shown by the solid line.
したがって、個々のＥＥＰＲＯＭについて、そのシフト
量を調べることは製品特性上、重要な要因である。Therefore, examining the shift amount of each EEPROM is an important factor in terms of product characteristics.
ところで、ＥＥＰＲＯＭの製造上、良品、不良品の製品
選別をする必要があるが、その手段として、ＥＥＰＲＯ
Ｍにデータを書き込んだり、消去した後、高温環境下に
保存して特性変化を調べる加速試験が一般に採用されて
いる。この加速試験によってＥＥＰＲＯＭのしきい値電
圧ｖｔｈのシフト量を調べるには、予め各ＥＥＰＲＯＭ
について、加速試験前のしきい値電圧Ｖ を測定してそ
のデータをコンピュータに記憶しておき、次に加速試験
後にしきい値電圧Ｖ をｆｆ１ｌＪ定し、試験前後のし
きい値電圧Ｖ の差からシフト量を求めることが可能で
ある。By the way, in manufacturing EEPROM, it is necessary to sort out good and defective products, and as a means of doing so, EEPROM
An accelerated test is generally used in which data is written or erased on M and then stored in a high temperature environment to examine changes in characteristics. In order to check the shift amount of the EEPROM threshold voltage vth by this accelerated test, each EEPROM
, measure the threshold voltage V before the accelerated test and store the data in the computer, then determine the threshold voltage V after the accelerated test, and calculate the difference between the threshold voltage V before and after the test. It is possible to obtain the shift amount from .
しかし、ＥＥＰＲＯＭはメーカにおいて大量生産される
ものであるから、個々のＥＥＰＲＯＭについて加速試験
前のしきい値電圧■ のデータを全てコンピュータに記
憶することはコンピュータに膨大な記憶容量が必要とな
る。そのため、従来は、一定の規格値を定め、加速試験
後（たとえば第４図の時刻ｔ。）のしきい値電圧Ｖ が
規格値以上であれば全て良品として取り扱い、しきい値
電圧ｖｔｈのシフト量までは測定していなかった。However, since EEPROMs are mass-produced by manufacturers, storing all threshold voltage data of each EEPROM before accelerated testing in a computer requires a huge storage capacity of the computer. Therefore, in the past, a certain standard value was established, and if the threshold voltage V after the accelerated test (for example, at time t in Fig. 4) was equal to or higher than the standard value, it was treated as a good product, and the threshold voltage vth was shifted. The amount was not measured.
〈発明が解決しようとする問題点〉
２のように、従来は、規格値のみで製品の良否を判断し
ており、しきい値電圧のシフト量に基づく良否の判断が
なされておらず、したがって、ＥＥＰＲＯＭの製品選別
の良否判断の際に十分な基準を与えているとは言えなか
った。<Problems to be Solved by the Invention> As mentioned in 2, conventionally, the quality of the product has been determined only based on the standard value, and the quality has not been determined based on the shift amount of the threshold voltage. It could not be said that sufficient standards were provided for determining the quality of EEPROM products.
本発明は、このような事情に鑑みてなされたものであっ
て、加速試験前後のＥＥＰＲＯＭのしきい値電圧のシフ
ト量が簡単に測定できるようにして、従来の規格゛値等
に加えてシフト量も製品選別判断基準の目安にできるよ
うにすることを目的とする。The present invention has been made in view of the above circumstances, and allows the shift amount of the EEPROM threshold voltage before and after the acceleration test to be easily measured. The purpose is to make it possible to use quantity as a guideline for product selection criteria.
く問題点を解決するための手段〉
本発明は、上記の目的を達成するために、新たに製造さ
れたＥＥＰＲＯＭの記憶領域の一部にユーザ非開放用の
専用領域を設ける一方、該ＥＥＰＲＯＭのしきい値電圧
を予め測定し、このしきい値電圧のデータを前記専用領
域に記憶した後、ＥＥＰＲＯＭの特性変化の加速試験を
行い、次に加速試験後のＥＥＰＲＯＭについて、しきい
値電圧を測定するとともに、予め前記専用領域に書き込
んでおいた加速試験前のしきい値電圧のデータを読み出
し、試験前後の両データからしきい値電圧のシフト量を
求めるようにしている。Means for Solving the Problems> In order to achieve the above object, the present invention provides a dedicated area that is not open to the user in a part of the storage area of a newly manufactured EEPROM, while After measuring the threshold voltage in advance and storing this threshold voltage data in the dedicated area, an accelerated test for changes in the characteristics of the EEPROM is performed, and then the threshold voltage is measured for the EEPROM after the accelerated test. At the same time, the threshold voltage data before the acceleration test written in advance in the dedicated area is read out, and the shift amount of the threshold voltage is determined from both the data before and after the test.
〈作用〉
本発明では、ＥＥＰＲＯＭ内に特性試験データを記憶す
る専用領域を設け、この専用領域に予め測定した加速試
験前のしきい値電圧のデータを記憶しておき、試験前後
のしきい値電圧からそのシフト量を求めるので、しきい
値電圧の規格値だけでなくシフト量も製品選別の判断基
準の目安にすることができる。<Function> In the present invention, a dedicated area for storing characteristic test data is provided in the EEPROM, and threshold voltage data measured in advance before an acceleration test is stored in this dedicated area. Since the amount of shift is determined from the voltage, not only the standard value of the threshold voltage but also the amount of shift can be used as a criterion for product selection.
〈実施例〉 以下、本発明を実施例に基づいて説明する。<Example> Hereinafter, the present invention will be explained based on examples.
本発明のＥＥＰＲＯＭの製品検査方法では、第１図のメ
モリマツプ図に示すように、新たに製造されたＥＥＰＲ
ＯＭの記憶領域Ｅの一部にユーザ非開放用の専用領域Ｅ
ｌを設け、残りの記憶領域Ｅ、がユーザの開放領域とし
て割り当てられる。In the EEPROM product inspection method of the present invention, as shown in the memory map diagram of FIG.
A dedicated area E that is not open to users is part of the OM storage area E.
1 is provided, and the remaining storage area E is allocated as an open area for the user.
このＥＥＰＲＯＭのしきい値電圧のシフト量を測定する
には、第２図のフローチャートに示すように、まず、ユ
ーザの開放領域Ｅ、のメモリセルに高電圧を印加して全
て“Ｉ”あるいは全て“０”のデータを書き込むととも
に、その際のしきい値電圧Ｖ をテスター等で測定する
。そして、測定したしきい値電圧Ｖ のデータを専用領
域Ｅ。To measure the amount of shift in the threshold voltage of this EEPROM, first, as shown in the flowchart of FIG. While writing data of "0", the threshold voltage V at that time is measured using a tester or the like. Then, the data of the measured threshold voltage V is stored in the dedicated area E.
に記憶する。たとえば、しきい値電圧Ｖ が５ｖであっ
た場合には、１１０のコードで表現された５ｖの値が専
用領域Ｅ、に記憶される。専用領域Ｅ１には、しきい値
電圧Ｖ のデータのみ書き込むので、記憶容量としては
たかだか数バイトあれば十分である。to be memorized. For example, if the threshold voltage V is 5V, a value of 5V expressed by a code of 110 is stored in the dedicated area E. Since only the data of the threshold voltage V 1 is written in the dedicated area E1, a storage capacity of at most several bytes is sufficient.
次に、このＥＥＰＲＯＭについて加速試験を行い、高温
環境下に保存する。そして、所定時間経過後に、予め専
用領域Ｅｌに書き込んでおいた加速試験前のしきい値電
圧（上記の例では５Ｖ）のデータを読み出し、次に、試
験後のＥＥＰＲＯＭについて、しきい値電圧Ｖ を再度
テスター等で測定する。続いて、試験前後の両データか
らしきい値電圧Ｖ のシフト量を求める。たとえば、試
験後に測定したしきい値電圧■ が４．５Ｖであれば、
そのシフト量ΔＶは０．５Ｖであることが分かる。Next, this EEPROM is subjected to an accelerated test and stored in a high temperature environment. After a predetermined period of time has elapsed, data on the threshold voltage before the acceleration test (5V in the above example) written in advance in the dedicated area El is read, and then the threshold voltage V of the EEPROM after the test is read out. Measure again using a tester, etc. Next, the shift amount of the threshold voltage V is determined from both data before and after the test. For example, if the threshold voltage ■ measured after the test is 4.5V,
It can be seen that the shift amount ΔV is 0.5V.
そして、このシフト量ΔＶに対して予め設定された許容
値と比較し、シフト量が許容値よりも大きければ不良品
、許容値よりも小さければ良品として選別する。Then, this shift amount ΔV is compared with a preset tolerance value, and if the shift amount is larger than the tolerance value, it is determined to be a defective product, and if it is smaller than the tolerance value, it is determined to be a good product.
〈発明の効果〉
以上のように本発明によれば、シフト量が簡単に測定で
きるので、製品選別の判断基準として、従来の規格値等
に加えてシフト量も目安にすることができるようになる
等の優れた効果が発揮される。<Effects of the Invention> As described above, according to the present invention, since the shift amount can be easily measured, the shift amount can be used as a criterion for product selection in addition to conventional standard values, etc. Excellent effects such as:
第１図および第２図は本発明の実施例を示し、第１図は
ＥＥＰＲＯＭのメモリマツプ図、第２図はＥＥＰＲＯＭ
の製品検査方法を説明するためのフローチャート、第３
図はＥＥＰＲＯＭのメモリセルの構成図、第４図はＩ、
ＥＰＲＯＭのしきい値電圧の経時変化を示す特性図であ
る。
ｌはコントロールゲート、２はフローティグゲート、３
はトンネル領域、４はソース、５はドレイン、６は基板
。1 and 2 show an embodiment of the present invention, FIG. 1 is a memory map diagram of an EEPROM, and FIG. 2 is a memory map diagram of an EEPROM.
Flow chart for explaining the product inspection method, Part 3
The figure is a configuration diagram of an EEPROM memory cell, and Figure 4 is I.
FIG. 2 is a characteristic diagram showing changes over time in threshold voltage of an EPROM. l is control gate, 2 is floating gate, 3
is a tunnel region, 4 is a source, 5 is a drain, and 6 is a substrate.
Claims (1)
にユーザ非開放用の専用領域を設ける一方、該ＥＥＰＲ
ＯＭのしきい値電圧を予め測定し、このしきい値電圧の
データを前記専用領域に記憶した後、ＥＥＰＲＯＭの特
性変化の加速試験を行い、次に加速試験後のＥＥＰＲＯ
Ｍについて、しきい値電圧を測定するとともに、予め前
記専用領域に書き込んでおいた加速試験前のしきい値電
圧のデータを読み出し、試験前後の両データからしきい
値電圧のシフト量を求めることを特徴とするＥＥＰＲＯ
Ｍの製品検査方法。(1) While providing a dedicated area that is not open to users in a part of the storage area of a newly manufactured EEPROM,
After measuring the threshold voltage of the OM in advance and storing this threshold voltage data in the dedicated area, an accelerated test for changes in EEPROM characteristics is performed, and then the EEPROM after the accelerated test is
For M, measure the threshold voltage, read the threshold voltage data before the accelerated test written in the dedicated area in advance, and calculate the shift amount of the threshold voltage from both data before and after the test. EEPRO featuring
M product inspection method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62274197A JPH01116999A (en) | 1987-10-29 | 1987-10-29 | Product inspecting method for eeprom |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62274197A JPH01116999A (en) | 1987-10-29 | 1987-10-29 | Product inspecting method for eeprom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01116999A true JPH01116999A (en) | 1989-05-09 |
Family
ID=17538385
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62274197A Pending JPH01116999A (en) | 1987-10-29 | 1987-10-29 | Product inspecting method for eeprom |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01116999A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001202799A (en) * | 1999-11-17 | 2001-07-27 | Motorola Inc | Measurement for threshold voltage distribution of memory array bit cell in circuit |
| JP2001266598A (en) * | 2000-03-22 | 2001-09-28 | Denso Corp | Test method for characteristics of non-volatile semiconductor memory |
| JP2005191434A (en) * | 2003-12-26 | 2005-07-14 | Toyota Central Res & Dev Lab Inc | Transistor, method for defining characteristics change model equation therefor and method for determining quality thereof |
-
1987
- 1987-10-29 JP JP62274197A patent/JPH01116999A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001202799A (en) * | 1999-11-17 | 2001-07-27 | Motorola Inc | Measurement for threshold voltage distribution of memory array bit cell in circuit |
| JP2001266598A (en) * | 2000-03-22 | 2001-09-28 | Denso Corp | Test method for characteristics of non-volatile semiconductor memory |
| JP2005191434A (en) * | 2003-12-26 | 2005-07-14 | Toyota Central Res & Dev Lab Inc | Transistor, method for defining characteristics change model equation therefor and method for determining quality thereof |
| JP4675043B2 (en) * | 2003-12-26 | 2011-04-20 | 株式会社豊田中央研究所 | Bipolar transistor, bipolar transistor characteristic variation model formula identification method, and bipolar transistor pass / fail judgment method |
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