JPS60242678A - Semiconductor memory device - Google Patents

Abstract

PURPOSE:To obtain an amorphous nonvolatile memory, which has excellent holding characteristics and reproducibility and a large area and large capacitance and cost thereof is low, by using an amorphous silicon carbide film in place of an amorphous silicon nitride film. CONSTITUTION:An insulating substrate 11, a lower electrode 12, an N<+> type 13, which is hydrogenated previously by amorphous silicon and to which phosphorus is doped to a high degree, and an N type 14 to which phosphorus is doped similarly to a low degree are formed in the order. An silicon oxide film 15 in which amorphous silicon in oxidized through plasma anodizing, etc., a film 16, which consists of a hydrogenated amorphous silicon carbide film and contains carbon by 35atom% or more, and an upper electrode 17 are shaped in the order. Accordingly, a device having performance, which has not exist as nonvolatile memories, such as, a holding time of ten years or more, a writing time of 0.1musec or less, even fast erasing speed, a large area and large capacitance and low cost is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a nonvolatile memory using amorphous, microcrystalline, or polycrystalline silicon (hereinafter referred to as amorphous silicon).

[Prior art]

The so-called NO8 structure, in which oxide and nitride are formed on a semiconductor substrate, is capable of high-density recording as a non-volatile memory.
It has many immediate advantages, such as the ability to easily rewrite the contents. For this purpose, a large amount of research has been conducted in recent years, including solid-state imaging/storage devices (IEICE technical report, KI 82-138) and video disks (Eng.
K Trans, onE, D,, ED728-854
) and other applications have been proposed. However, as long as crystalline silicon is used as the semiconductor substrate, it is difficult to increase the area and increase the capacity, and the cost becomes extremely high. Therefore, it has been proposed to use amorphous 7-licon as a substrate, which can be made large in area at low cost (IEICE technical report, 5SD
-83-28). In a metal-nitride film-oxide film-semiconductor substrate type (hereinafter abbreviated as MNOS) diode, the characteristics of the nitride film have a large influence on the memory write characteristics and retention characteristics. Furthermore, as long as amorphous silicon or the like is used for the substrate, it is inappropriate to use a process at high temperature due to the release of hydrogen, etc., and therefore deposition of an amorphous silicon nitride film by plasma decomposition is used. However, silicon nitride films produced by plasma decomposition vary greatly depending on the deposition conditions.
The 191/N ratio is different from the chemical equivalent ratio.

As a result, the coupling becomes incomplete and the film quickly becomes a low-resistance nitride film, which poses a major problem in terms of retention characteristics and reproducibility as an MNOS diode.

In order to make the amorphous silicon nitride film high in resistance, it is possible to increase the high-frequency power for plasma decomposition or to raise the substrate temperature during deposition, but the former requires a thicker device and is more expensive, and the latter increases the substrate temperature. This has a negative effect on amorphous silicon, which causes problems in reproducibility as a memory.

〔the purpose〕

To provide an amorphous nonvolatile memory which has excellent retention characteristics and reproducibility, has a large area, has a large capacity, and is low in cost, by completely eliminating these drawbacks. For all purposes.

〔overview〕

That is, the amorphous silicon nitride film (hereinafter, a-8iN
It is abbreviated as ) instead of an amorphous silicon carbide film (hereinafter a-
It is abbreviated as 8iC. ), it is possible to provide an amorphous nonvolatile memory that quickly reaches T'.

〔Example〕

FIG. 1 is a sectional view of an amorphous nonvolatile memory according to an embodiment of the present invention. 11 is an insulating substrate such as glass or quartz; 12 is a lower electrode such as aluminum, molybdenum, chromium, or To; 15 and 14 are hydrogenated amorphous silicon;
13 is a highly phosphorus-doped r3+ type, 14 is a lightly phosphorus-doped n-type, and the model thicknesses are 100~2000X and 2000~n, respectively.
20,000λ, 15 is a silicon oxide layer that has been completely oxidized by plasma anodization etc. and has a thickness of 5~
100X, 16 is a hydrogenated amorphous silicon carbide film with a carbon content of 35 atoms or more, and a thickness of 300 to 300 mm.
X and 17 are upper electrodes made of aluminum, molybdenum, chromium, ■To, or the like.

13, 14, and 16 are all deposited using the plasma decomposition method*, and 13 to 16 can be deposited in the same vacuum chamber without breaking the vacuum (hereinafter, devices with this structure will be referred to as MOOS memories. ).

Here, the deposition conditions for a-BlC used in the present invention will be compared with the general deposition conditions for a, -8iN conventionally used (shown in Table 1).

Table 1 Differences in Deposition Conditions As is clear from Table 1, a-81C@ generally requires a lower deposition temperature and an order of magnitude less high-frequency power. Furthermore, since the deposition rate of A-8'10 is faster, the cost is very low, and an apparatus on the scale of IJX is sufficient. Also, regarding the resistivity of the film produced under the conditions shown in Table 1, a-8iC has a high resistance equal to or higher than that of a-8i and N.

Furthermore, the electrical characteristics are shown in FIGS. 2 and 3.

FIG. 2 shows an example of a shift in the capacity versus voltage curve of a nonvolatile memory (MC!OS memory) using a-8iC according to the present invention, 21 is the curve before writing, 22 is 1.
This is a curve after Nordic writing with a width of 0μ and a height of 15V. A writing time of 1.0 μm is sufficient. Memory using a7siN for comparison (MNo s memory)
An example of the shift of the capacitance vs. voltage curve is shown in FIG. 41 is the curve before writing, 42 is 1.0 sec wide and 1 high.
This is a curve after 5V Norculus writing. Conventional a-I
Even with memory using EiN, the write time is 1.0μ (6
), but when comparing the amount of shift before writing, it is clear that the memory using a-6iO according to the present invention is thicker, and the memory according to the present invention can write at even faster speeds. Can respond to Write times required for non-volatile memory are short (at least 1
．． The example according to the present invention fully satisfies the condition of 0μ or less) and can also respond satisfactorily to a shorter writing time of cL1 to Q, 01μ.

As a non-volatile memory, retention time is a more important requirement than write time. The retention time should be as long as possible, preferably several years or more. FIG. 6 shows the flat band voltage of the device of the invention versus elapsed time. The writing conditions were a pulse with a width of 1.0μ and a height of 15V, and the subsequent standing time was plotted on the horizontal axis. Since the flat band voltage before writing is about 2V, the retention time (here, the time when the flat band voltage reaches the initial voltage IA due to the difference from the above 2V) is 10 years from the graph 31 in Figure 3. (5600
date) or more, and can be used satisfactorily as a non-volatile memory. MNOE using conventional a-8iN for comparison
FIG. 5 shows the retention time characteristics in type I memory. 51
The write pulse is 15V1 width 1.0μ as in Figure 3.
If the retention time is 100 days or less, the writing pulse should be set to 15V9 with a width of 5.5μ and the third
As shown in Figure 52, even if the initial flat band voltage is the same as the device of the present invention (approximately 4 V), the holding time is 1000 days (2
, 7th grade) and below. Furthermore, the device according to the present invention can be erased in a shorter time than the amorphous N'MO8 type.

As mentioned above, an example of the electrical characteristics of the device used in the present invention is shown in FIG.
The silicon oxide film of No. 5 had a thickness of 35X, and the amorphous silicon carbonized pancreas of No. 16 had a carbon content of 75 atoms and a thickness of 850X. Regarding film thickness and carbon content, it is the first
Although good characteristics can be obtained within the range of numerical values used when explaining the figures, the examples of electrical characteristics show relatively good ones within that range. In addition, in Figure 1, 16 carbide films contain elements from group II of the periodic table, such as boron and gallium, from 11 ppB to 1.
By adding about 7 ppm to 100 pp.%, the retention time is long9, and as a result, it can be retained for several years even when written with short pulses. Excellent results can be obtained by selecting carbonization conditions in which the carbon content of the 16 carbonized films in FIG. 1 is 35 atomic percent or more, particularly 50 atomic percent to 85 atomic percent.

〔effect〕

As shown in the above examples, the amorphous silicon nonvolatile memory using a-8iC has a retention time of 10 years or more, a write time of 0.1 μx or less, a fast erase speed, and a large area, large capacity, and This device is low cost and has unprecedented performance as a non-volatile memory.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the memory structure of the present invention. Figures 2 and 3
The figure is an electrical characteristic diagram of the amorphous memory of the present invention. FIGS. 4 and 5 are electrical characteristic diagrams of conventional amorphous memories. Above is Figure 1. Mark 80 Den Fi (V) Fig. 2 Keieho (Q) Mark tIrIIJi (v) Fig. 4 Shikaku Himaki (Japanese)

Claims (1)

[Claims] (1) Amorphous silicon, microcrystalline silicon, or polycrystalline silicon is formed in contact with the conductive electrode provided on the insulating substrate, and a Noricon oxide film is entirely formed, and a carbon content of 35 atomic particles is formed on the oxide film. Amorphous, microcrystalline or a of 1 cent or more
A semiconductor memory device characterized in that a polycrystalline silicon carbide film is formed. (2. The amorphous, microcrystalline, or polycrystalline silicon carbide model described in claim 1, including boron, gallium, and other elements of group II of the periodic table, all α111) I) m to 100 p p
, m is added to the semiconductor memory device.