JP2000003948A - Non-volatile memory device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a non-volatile memory element which is subjected to reformation and prevented from deteriorating in data holding properties before delivery. SOLUTION: After a memory device is subjected to a data holding property test (step S4) in a wafer state, test data are rewritten to data of reverse pattern (step S6). Thereafter, a package sealing process is carried out (step S8). Then, conditions of a data holding property test carried out after packaging area set (step S10). A condition setting is carried out by calculating a data pattern, a heating temperature, and a heating time in a following storage state heating process resting on stress calculated for each data pattern as to the steps S4 and S8 which are previously carried out. Conditions for a following storage state heating process are set so as to make the total sum of stress of each data pattern as equal to each other as possible, whereby a ferroelectric memory can be less reformed through all storage state heating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonvolatile memory device and a method of manufacturing the nonvolatile memory device, and more particularly, to an improvement in data retention characteristics of the nonvolatile memory device.

[0002]

2. Description of the Related Art A non-volatile memory is known as a semiconductor memory capable of retaining data even when power is turned off. In a manufacturing process of a nonvolatile memory, a data retention characteristic test is generally performed. In the data retention characteristic test, the data is stored in each memory element constituting the nonvolatile memory as data.
This is performed to write “0” or “1” to check how long each memory element can hold the written data.

The period during which a memory element can hold written data is extremely long. On the other hand, when the memory element is heated, the period during which data can be held is shortened. Therefore, the data retention characteristic test is performed under heating to shorten the test period.

[0004]

However, the conventional manufacturing process of the above-mentioned nonvolatile memory has the following problems. In the conventional manufacturing process of a nonvolatile memory, as shown in FIG. 6, first, test data is written into the nonvolatile memory (step ST2), and a data retention characteristic test is performed under heating in a wafer state (step ST2). ST4). The package sealing step is performed while the data written during the data retention characteristic test is retained (step ST6). The package sealing step is also performed under heating.

After the package sealing step, a data retention characteristic test is performed again (step ST8). In this data retention characteristic test, the same data as the data written in the data retention characteristic test in the state of the wafer previously performed is written in each memory element.
Under heating, a data retention property test is performed. Therefore, each memory element holds the same data while holding the same data.
The heating process will be repeated twice.

[0006] On the other hand, it is known that there is a memory element to which "having effect" is performed, such as a memory element using a ferroelectric substance. The customization means that the same data (for example, “1”) is held and the data that is opposite to the held data (“0” in the above example) is held by being left or heated for a long period of time. This refers to a phenomenon in which the retention characteristics deteriorate.

[0007] For this reason, in the memory element subjected to such shaving, there is a possibility that data retention characteristics may be deteriorated before shipment depending on the above-mentioned conventional non-volatile memory manufacturing process.

The present invention solves the problem of such a conventional method of manufacturing a nonvolatile memory device such as a nonvolatile memory, and provides a nonvolatile memory device which is subjected to “having” a data retention characteristic before shipment. It is an object of the present invention to provide a nonvolatile memory device with less deterioration and a method for manufacturing the same.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a nonvolatile memory device, wherein a data holding characteristic corresponding to each value of data to be stored stores the value and data of the stored data. What is claimed is: 1. A method for manufacturing a nonvolatile memory device having a storage element which is affected by an applied temperature in a state where time and data are stored, comprising: Provided above,
The storage data value in at least one storage state heating step is different from the storage data value in another storage state heating step.

According to a second aspect of the present invention, there is provided a method of manufacturing a nonvolatile memory device according to the first aspect.
By adjusting one or both of the time during which the data is stored and the temperature applied while the data is stored in at least one storage state heating step, each value of the data to be stored is adjusted. Data retention characteristics that are configured to be closer to each other,
It is characterized by.

According to a third aspect of the present invention, in the method for manufacturing a nonvolatile storage device according to the first or second aspect, at least one of the storage state heating steps is a data retention characteristic test. , Is characterized.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a nonvolatile memory device according to any one of the first to third aspects, wherein the nonvolatile memory device comprises a ferroelectric material. And a storage element using the same.

According to a fifth aspect of the present invention, in the nonvolatile storage device, the data holding characteristic corresponding to each value of the data to be stored stores the value of the stored data, the time during which the data is stored, and the data. A non-volatile storage device having a storage element that is affected by the temperature applied in step 2, wherein the storage element is heated in a state where data is stored in two or more steps, and the value of the stored data in at least one of the steps Is set to a value different from the value of the stored data in the other steps.

According to a sixth aspect of the present invention, in the nonvolatile storage device, the data holding characteristic corresponding to each value of the data to be stored stores the value of the stored data, the time during which the data is stored, and the data. A non-volatile storage device having a storage element affected by the temperature applied thereto, characterized in that data storage characteristics corresponding to respective values of data to be stored are made substantially the same.

[0015]

According to the first aspect of the present invention, there is provided a method of manufacturing a nonvolatile storage device, comprising: storing a value of storage data in at least one storage state heating step; Characterized in that it is configured to be different from the value of.

Therefore, compared to the case where the value of the stored data is the same in all the storage state heating steps, the memory element is less likely to be deformed. Therefore, the data holding characteristics corresponding to the respective values of the data to be stored are closer to each other. That is, it is possible to prevent the data retention characteristics from deteriorating before shipment.

According to a second aspect of the present invention, in the method of manufacturing a non-volatile memory device, the data storage time is adjusted by adjusting one or both of the data storage time and the temperature in the storage state heating step. The data holding characteristics corresponding to the respective values are configured to be closer to each other.

Therefore, it is possible to adjust the conditions of the storage state heating step so that the memory elements are less likely to be habituated. For this reason, the data holding characteristics corresponding to the respective values of the data to be stored are closer to each other. That is, it is possible to further prevent the data retention characteristics from deteriorating before shipment.

According to a third aspect of the present invention, in the method for manufacturing a nonvolatile storage device according to the first or second aspect, at least one of the storage state heating steps is a data retention characteristic test. It is characterized by.

Therefore, in the data retention characteristic test performed at a high temperature, the habit of the memory element is not accelerated. That is, even in a nonvolatile storage device that requires a data retention characteristic test, it is possible to prevent the data retention characteristic from deteriorating before shipment.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a nonvolatile memory device according to any one of the first to third aspects, wherein the nonvolatile memory device comprises a ferroelectric material. Characterized by having a storage element using

Therefore, even in a memory element using a ferroelectric material which is apt to cause habit, the habit can be reduced. That is, even in a non-volatile storage device having a storage element using a ferroelectric material that is apt to cause habit, deterioration of data retention characteristics before shipment can be prevented.

According to a sixth aspect of the present invention, the nonvolatile storage device is characterized in that data holding characteristics corresponding to respective values of data to be stored are substantially the same.

Therefore, the data holding characteristic becomes almost constant irrespective of the value of the data to be stored. That is, a nonvolatile storage device with high data retention characteristics can be realized.

[0025]

FIG. 1 is a flowchart showing a part of a method of manufacturing a ferroelectric memory (hereinafter abbreviated as "memory") as a method of manufacturing a nonvolatile primary memory device according to an embodiment of the present invention. Shown in form.

As shown in FIG. 1, first, test data, which is storage data, is written in a ferroelectric memory in a state of a wafer (step S2). The test data is given in a binary pattern such as “0100101110...”, And each bit of the binary number is stored in each ferroelectric memory element constituting the ferroelectric memory. For convenience, the above-described test data pattern is referred to as a first pattern.

Next, while the test data of the first pattern is written, a data retention characteristic test, which is a heating step of a storage state, is performed (step S4). The data retention characteristic test is performed by leaving the wafer under heating for a certain period of time and then inspecting whether or not the ferroelectric memory retains data.

Next, the data of the first pattern written in the ferroelectric memory in step S2 is rewritten to the data of the reverse pattern (step S6). For example, step S
The ferroelectric memory element in which “0” is written in 2 is rewritten to “1”. The above example ("010010"
1110...) Is rewritten to a pattern of “1011010001...” For convenience, this pattern of test data is referred to as a second pattern.

Next, a package sealing step, which is a storage state heating step, is performed (step S8). In the package sealing step, heat is applied to the ferroelectric memory while retaining the data of the second pattern.

Next, the next storage state heating step is as follows:
The conditions for the data retention characteristic test after packaging are set (step S10). The step S10 is described in detail in FIG. In this step, first, as shown in FIG. 2, in the storage state heating step already performed, that is, in the data holding characteristic test in the wafer state in step S4 and the package sealing step in step S8, stress is applied to each data pattern. (Step S10)
2).

[0031] for each data pattern, indicating an equation for calculating the _{stress, S1 = Σ i = 1,} n (D1 i × exp (Ea / k × (1 / Ta-1 / Tb1 i))) S2 = Σ i _{= 1, m (D2 i ×} exp (Ea / k × (1 / Ta-1 / Tb2 i))) ... equation 1.

In the above formula, S1: stress in the first pattern S2: stress in the second pattern n: number of heating steps in the already-stored storage state holding the first pattern m: heating in the already-stored storage state holding the second pattern Number of steps D1 _i : heating time of the ith memory state heating step holding the first pattern D2 _i : heating time of the ith memory state heating step holding the second pattern Tb1 _i : _i- th holding the first pattern Heating temperature (absolute temperature) of the memory state heating step Tb2 _i : Heating temperature (absolute temperature) of the i-th memory state heating step holding the second pattern Ea: Activation energy of the material constituting the ferroelectric memory element k: Boltzmann constant (8.62 × 10 ⁻⁵ eV / ゜ K) Ta: room temperature (absolute temperature). Here, Σ _{i = 1, h} (C _i ) = C ₁ + C ₂ + ... + C _h
Represents

Next, the data pattern, the heating temperature, and the heating time for the data retention characteristic test after packaging, which is the next storage state heating step, are set (step S104).

The calculated difference d in the stress of each data pattern
S dS = (S1−S2) is calculated, and the data pattern of the data retention characteristic test after packaging is set according to the sign of dS. For example, dS
Is positive, the data pattern of the data retention characteristic test after packaging is set to the second pattern. Next, based on the absolute value of dS, a data pattern, a heating temperature, and a heating time of a data retention characteristic test after packaging are set.
For example, when the data pattern of the data retention characteristic test after packaging is set to the second pattern, the stress S2 _{m + 1} generated in the ferroelectric memory by the data retention characteristic test after packaging is the difference between the stress calculated above. The heating temperature Tb2 _{m + 1} and the heating time D2 _{m + 1} so as to be as close as possible to dS.
Make the settings for

The stress S2 _{m + 1} generated in the ferroelectric memory by the data retention characteristic test after packaging is expressed by the following equation: S2 _{m + 1} = D2 _{m + 1} × exp (Ea / k × (1 / Ta− 1 / Tb2
_{m + 1} )).

After the conditions for the data retention characteristic test after packaging, which is the next storage state heating step, are set as described above, the test set in step S104 is applied to the ferroelectric memory as shown in FIG. Data is written (step S12).

Next, a data retention characteristic test after packaging is performed under the heating temperature Tb2 _{m + 1} and the heating time D2 _{m + 1} set in step S104 (step S14). In this way, by setting the conditions of the storage state heating step so that the total sum of the stresses for each data pattern is as equal as possible, it is possible to reduce the “habit” in the storage state heating step.

FIG. 7 shows a sectional structure of a ferroelectric memory which is a nonvolatile memory device manufactured by the above method.
The ferroelectric memory is formed on a channel region CH formed between a source S and a drain D provided on a substrate SB.
The gate oxide film GM made of an insulator, the floating gate FG made of a conductor, the ferroelectric layer FM made of a ferroelectric, and the control gate CG made of a conductor are It is configured to stack in order. Wirings SE and DE are connected to the source S and the drain D, respectively.

As described above, this ferroelectric memory is adjusted so that the sum of stresses for each data pattern is as equal as possible. Therefore, the data holding characteristics corresponding to each value of the data to be stored are almost the same.

In the above-described embodiment, in step S6, the data of the first pattern written in the ferroelectric memory in step S2 is configured to be rewritten with the data of the reverse pattern.
It is also possible to execute the processing of step S8 and subsequent steps without rewriting the data of the first pattern written in the ferroelectric memory.

In step S10, the sum of the stresses in both the storage state heating processes in steps S4 and S8 is calculated, and based on this, the condition of the third storage state heating process is calculated. Each time the heating step is completed, the condition of the next storage state heating step may be determined.

FIG. 3 is a flowchart showing a part of a method for manufacturing a ferroelectric memory according to another embodiment of the present invention.

The method of manufacturing the ferroelectric memory shown in FIG.
First, after setting the conditions for all the stored state heating steps, one or more stored state heating steps are performed without setting the conditions, in that each stored state heating step is performed according to the set conditions. Thereafter, the method differs from the method for manufacturing a ferroelectric memory shown in FIG. 1 in which the conditions for the next storage state heating step are determined based on the stress caused by these processed storage state heating steps.

In this manufacturing method, as shown in FIG. 3, first, conditions of all assumed storage state heating steps are set (step S22). The conditions of the storage state heating step are set so that the stress S1 and the stress S2 calculated by the equation 1 are equalized as much as possible, and the test data patterns, D1 _i , Tb1 _i , and D2 in each storage state heating step are set.
i, Tb2 _i are set.

In the equation (1), n represents the total number of stored state heating steps holding the first pattern, and m represents the total number of stored state heating steps holding the second pattern.

Next, based on the conditions set in step S22, each test data is written (step S24,
S28, S32) and the processing of each storage state heating step (steps S26, S30, S34) are executed.

FIG. 4 is a flowchart showing a part of a method for manufacturing a ferroelectric memory according to still another embodiment of the present invention.

The method of manufacturing the ferroelectric memory shown in FIG.
The method differs from the method for manufacturing a ferroelectric memory shown in FIG. 1 in that a storage state heating step indispensable in a manufacturing process is only a data retention characteristic test after packaging. 1 is different from the method of manufacturing a ferroelectric memory shown in FIG. 1 in that a dummy heating step for heating only is provided.

In this manufacturing method, as shown in FIG. 4, first, test data is written into the ferroelectric memory (step S42), and then a data retention characteristic test after packaging is performed (step S44). ).

Next, the conditions for the heating step of the dummy storage state are set (step S46), and the data pattern of the ferroelectric memory is rewritten with the reverse pattern data (step S4).
8) A dummy heating step is performed according to the conditions obtained in step S46 (step S50). Steps S46 to S50 in this manufacturing method correspond to steps S10 to S14 in the method for manufacturing a ferroelectric memory shown in FIG.
This is almost the same procedure.

In this manufacturing method, as shown in FIG. 4, the only memory state heating step essential for the manufacturing process is step S44. Therefore, if the dummy heating step is not provided, only one data pattern is held in the storage state heating step, and the stress is biased to one data pattern. This is prevented, and the stress is distributed to each data pattern, thereby preventing “habitation” in the storage state heating step.

In this embodiment, the case where the number of storage state heating steps indispensable in the manufacturing process is one has been described as an example. A dummy heating step can be provided. For example, in the embodiment shown in FIG. 1, a dummy heating step is added before and after step S14 if the stress in the already-processed stored state heating step cannot be dispersed by only the storage state heating step in step S14 for some reason. can do.

Next, FIG. 5 is a flowchart showing a part of a method for manufacturing a ferroelectric memory according to still another embodiment of the present invention. The method for manufacturing a ferroelectric memory shown in FIG. 5 differs from the method for manufacturing a ferroelectric memory shown in FIG. 1 in that a step for setting conditions for the next storage state heating step is not particularly provided.

As shown in FIG. 5, in this manufacturing method, similarly to the manufacturing method shown in FIG. 1, test data is written to the ferroelectric memory (step S62), and a data holding characteristic test in a wafer state (step S64). , Rewriting test data to reverse pattern data (step S6)
6) A package sealing step (Step S68) is performed.

Next, without setting the conditions for the next storage state heating step, the data pattern of the ferroelectric memory is
The data pattern is returned to the data pattern set in step S62 (step S70), and a data retention characteristic test after packaging is performed (step S72).

With this configuration, the stress of each data pattern can be dispersed to some extent without setting conditions for the next storage state heating step that requires complicated calculations.

In each of the above-described embodiments, the case where at least one of the storage state heating steps is a data retention characteristic test has been described as an example. Even when not including, it can be applied.

Although the case where the nonvolatile memory device is a ferroelectric memory has been described as an example, the present invention can be applied to a case where the nonvolatile memory device is other than a ferroelectric memory.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a part of a method of manufacturing a ferroelectric memory, which is a method of manufacturing a nonvolatile primary storage device according to an embodiment of the present invention.

FIG. 2 is a detailed flowchart of a process of step S10 in FIG. 1;

FIG. 3 is a flowchart showing a part of a method of manufacturing a ferroelectric memory according to another embodiment of the present invention.

FIG. 4 is a flowchart showing a part of a method of manufacturing a ferroelectric memory according to still another embodiment of the present invention.

FIG. 5 is a flowchart showing a part of a method of manufacturing a ferroelectric memory according to still another embodiment of the present invention.

FIG. 6 is a flowchart showing a part of a conventional method of manufacturing a ferroelectric memory.

FIG. 7 is a diagram showing a part of a cross-sectional structure of a ferroelectric memory which is a nonvolatile primary storage device according to an embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 29/792

Claims (6)

[Claims] 1. A data holding characteristic corresponding to each value of data to be stored, the value of the stored data, the time during which the data is stored, and the influence of the temperature applied in a state where the data is stored. A method of manufacturing a non-volatile storage device having a storage element for receiving, wherein two or more storage state heating steps for heating while storing data are provided, and a value of storage data in at least one storage state heating step A method different from the value of the storage data in the other storage state heating step. 2. The method for manufacturing a nonvolatile memory device according to claim 1, wherein at least one of a storage state heating step includes a time for storing data and a temperature applied in a state for storing data. Or by adjusting both of them to make the data holding characteristics corresponding to each value of data to be stored closer to each other. 3. The method for manufacturing a nonvolatile memory device according to claim 1, wherein at least one of the storage state heating steps is a data retention characteristic test. 4. The method for manufacturing a nonvolatile memory device according to claim 1, wherein the nonvolatile memory device has a storage element using a ferroelectric material. What to do. 5. A data holding characteristic corresponding to each value of data to be stored, the value of the stored data, the time during which the data is stored, and the influence of the temperature applied in the state where the data is stored. A non-volatile storage device having a storage element for receiving data in at least two steps, wherein the storage element is heated while storing data, and the value of the storage data in at least one of the steps is:
A value different from the value of the storage data in the other steps described above. 6. A data holding characteristic corresponding to each value of data to be stored, the value of the stored data, the time during which the data is stored, and the influence of the temperature applied in the state where the data is stored. A non-volatile storage device having a storage element for receiving data, wherein data storage characteristics corresponding to respective values of data to be stored are configured to be substantially the same.