JPH041931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor memory device for constructing a nonvolatile optical memory using a non-single crystal semiconductor including an amorphous structure.

This invention contains germanium or silicon to which hydrogen and oxygen are added as a main component, and impurities selected from groups or groups of the periodic table.
×10 ¹⁶ to 1 × 10 ²¹ cm ^-3 doped non-single crystal semiconductor, irradiated with short wavelength light of 600 nm or less,
The process of writing memories by reducing the electrical conductivity of this semiconductor, and conversely, increasing the electrical conductivity of this semiconductor using infrared radiation of 5 μ or more (~50 μ) or heat treatment at 120 to 300°C to rewrite memories. An object of the present invention is to propose a rewritable nonvolatile semiconductor memory device having a process of performing the following steps.

This invention actively utilizes the reduction in electrical conductivity caused by light irradiation, conventionally known as the Stebla-Lonski effect (light irradiation effect), which is a deterioration phenomenon that is particularly bad for semiconductor devices in general, especially for photoelectric conversion devices. It is characterized by providing a rewritable memory device. That is, it has been known that when a photoelectric conversion device is manufactured using amorphous silicon, the photoelectric conversion device deteriorates due to light irradiation and its electrical conductivity decreases. . The inventor investigated this factor in detail and found that in non-single-crystal semiconductors whose main components are silicon and germanium, the density of recombination centers (referred to as "within Eg") existing in the forbidden band (referred to as "within Eg") of the energy band (referred to as "Eg") It was found that this was caused by an increase or decrease in RC (hereinafter referred to as RC). Furthermore, it was revealed that in this semiconductor, for example, a silicon semiconductor, oxygen and hydrogen create OH groups, which combine with or separate from silicon dangling bonds, increasing or decreasing the number of recombination centers. We were able to.

As a model, A reversible reaction process is proposed. That is, the D ⁰ level changes to D ⁻ or D ⁺ by irradiation with short wavelength light.
That is, the reaction changes to the left in the above equation. the result,
Deep RC is formed within Eg. This RC reduces electrical conductivity. However, D ^- and D ⁺ reversibly change to D ⁰ by far-infrared light or heat treatment. The present invention actively utilizes the property that RC reversibly increases or decreases.

For this reason, oxygen and hydrogen are actively added to the intrinsic semiconductor or substantially intrinsic semiconductor (hereinafter simply referred to as a layer or type semiconductor) of the present invention. Specifically, oxygen is 1×10 ²⁰ to 5×10 ²¹ cm ^-3
For example, 5×10 ²⁰ cm ^-3 , and hydrogen was contained in an amount of 5 to 30 atom %, for example, 15 atom %.

Furthermore, for such a reversible reaction, it is necessary to shift the Fermi level to some extent from the conduction band and convert it to N ^- .
It was found that the reversible process between D ^- , D ⁺ , and D ⁰ was established and is effective. That is, the activation energy is preferably 0.3 to 0.7 eV for amorphous silicon.
It was set to 0.4 to 0.6 eV. For this reason, groups of the periodic table (sodium, potassium, etc.), groups (nitrogen, phosphorus,
Arsenic, antimony, etc.) were used. Typically Na,
K, N, P.

In the present invention, to read out the stored information, visible light of a specific intensity (100 to 10,000 lx) is applied to a specific address using a spot of 1 to 100 μφ, for example, 5 μφ, such as an Ar laser (514.5 n
m, 488nm), He-Ne laser (using 632.8nm)
It is irradiated with 0 and 1 depending on the electrical resistance of the address.

That is, in the semiconductor device of the present invention, the first and second electrodes are surface electrodes, and electric energy is applied to the entire surface of the semiconductor. However, in order to specify the address, light irradiation is performed on the predetermined address in the form of a spot (1 to 100 μφ, e.g. 5 μφ), and the sensitivity of the electrical conductivity at that address is measured in other areas (areas of the disk where the light is not irradiated). ) compared to 10 ² to 10 ⁴ .

By checking the electrical conductivity at that location, it was possible to read the memory at any address. With this configuration, it has become possible to create a nonvolatile memory that can read out electrical signals with optical assistance. Therefore, by reducing the size of this light spot, 1
〜10 ⁴ Gbit memory is now possible, and it has great applications in optical disks, etc. In particular, its component is silicon, which is inexpensive, is not a polluting material, and can be used in expensive materials such as tellurium oxide or magneto-optical disks. By not using it, it has the great advantage of reducing costs and improving optical reliability.

Furthermore, to write data in the semiconductor memory device of the present invention, a short wavelength light of 600 nm or less, such as a nitrogen laser (337 nm), is irradiated to a predetermined address with a spot of 1 to 100 μφ, and the address that was initially “0” is selected. changed to "1". Also, to rewrite the memory, the temperature must be 120 to 300℃ to set everything on this disk to "0".
We were able to stably create "0" by thermal annealing, for example, at 150°C for 30 minutes. For selective rewriting, long wavelength light of 5 microns or more (1 to 30 microns, preferably 10.8 microns) may be irradiated to locally heat and anneal only a predetermined address. In this way, it is possible to write and rewrite memory only by irradiating light, and it has the feature that large-capacity processing is possible.

The present invention proposes a non-contact type semiconductor memory device that makes optical reading possible by utilizing the increase and decrease in electrical conductivity of semiconductors.

The contents are described below according to the drawings.

Figure 1 shows a transparent conductive film (referred to as CTO) electrode 3 on a transparent insulating substrate 4, the main component of which is tin oxide to which a halogen element is added. Indium (hereinafter referred to as ITO)
) and tin oxide selectively (E
1) was formed. Furthermore, a first non-single crystal semiconductor (here, N type) 5, a second non-single crystal semiconductor (here, I type) 6, and a third non-single crystal semiconductor (here, P type) 7 are stacked. A counter electrode 2 (hereinafter referred to as E2) of a semiconductor 1 having a PIN structure (referred to as S) and a second electrode having transparent light-transmitting properties such as ITO 3-S1-E2 2
A longitudinal cross-sectional view of the structure is shown.

In the drawings, a semiconductor 1 is manufactured by first using silane (SinH), a silicide gas with n>1, by a plasma glow discharge method (PCVD method) or a light plasma CVD method.
It is formed to have a thickness of 10μ, for example 3μ. In the drawing, the first semiconductor 5 is of P type and has a structure of H ₂ Si(CH ₃ ) ₂ /(SiH ₄ +
H ₂ Si (CH ₃ ) ₂ ) = 0.2 to 0.7, for example 0.5, and B
10 ¹⁶ ~ 1×10 ²² cm ^-3 by B ₂ H _{6 etc.}
By adding B ₂ H ₆ /SiH ₄ =0.5%, SixC _1-X 0
<x<1 x=0.8. The second semiconductor is an I-type semiconductor, in which in addition to reducing the change in impurities of B, Na, K, P, and N are added at 5×10 ¹⁶ to 1×10 ²¹ cm ^-3
Added. For example, 5×10 ¹⁹ cm ⁻³ of N was added. Furthermore, this semiconductor is changed to Na or K to NaCl or KCl.
(0.1N water temperature is 100°C) for about 10 minutes, and the added impurity was set to, for example, 1×10 ²⁰ cm ^-3 . This was dried to form an N-type semiconductor on the upper surface.

In addition, the third semiconductor is N type, and H ₂ Si (CH ₃ ) ₂ /
(SiH ₄ + H ₂ Si (CH _{3 ) 2} ) = 0.05 to 0.5, for example, 0.1, and P at the same time to 10 ¹⁶ to × 10 ²² cm ^-3 , for example, PH
₃ /SiH ₄ = 1% and formed in the semiconductor 1.
A PIN junction was constructed.

This semiconductor film can be manufactured using sputtering method, vacuum evaporation method, light plasma CVD method, LT (low temperature) CVD method (HOMO
(also referred to as CVD method) or reduced pressure CVD method may be used.

Further, before and after the process of forming this semiconductor, electrodes 3 and 2 made of transparent electrodes were formed by a known vacuum evaporation method, plasma CVD method, or low pressure CVD method to obtain the structure shown in FIG.

An energy band diagram corresponding to the structure shown in FIG. 1 is shown in FIG.

In this energy band diagram, the active energy region 14 of the I-type semiconductor is 0.3 to 0.7 eV, for example, 0.5 eV.
It has an N-type conductivity type. Further, the electrons 19 flowing in the conduction band 11 and the holes 18 flowing in the valence band 12 of the semiconductor 6 recombine with each other via the RC 13 present in the I-type semiconductor 6.

There are two types of RC: one that occurs and disappears due to the above-mentioned light irradiation effect, and the other that is caused by unpaired bonds in silicon that do not change. However, this RC17,B
When the number increases, electrons and holes recombine 13, resulting in poor electrical conductivity. This change in electrical conductivity is shown in FIG.

In the drawings, "1" indicates high electrical conductivity due to thermal annealing, and "0" indicates low electrical conductivity due to irradiation with short wavelength light. Further, curve 13'' is the dark conductivity, and curve 15'' is the optical conductivity of AM1 (100 mW/cm ² ). 14 indicates the electrical conductivity when irradiated with light using an argon laser. Furthermore, as is clear from the drawings, curves 13 and 15 could be obtained by adding phosphorus thereto to increase the amount.

That is, by irradiating the light, the S/N ratio of "0" and "1" was increased by nearly an order of magnitude. 44,4
5 has "1" and "0" respectively at the time of reading, and it can be seen from the reversible change that writing is possible.

Although this figure 1 shows the case of amorphous silicon, it is also possible to cause reversible changes in non-single crystal compounds or mixture semiconductors such as Ge and GexSi _1-X (0<x<1). .

It goes without saying that the term "semiconductor" as used in the present invention includes semiconductors to the extent that current can flow therethrough.
Furthermore, in the present invention, when high voltage pulsed light is applied, the electrodes 2 and 3 and the semiconductors 5 and 7 in FIG.
Reactions at the interface with the material also occur during long-term use,
Insulating silicon oxide is formed at the interface, resulting in deterioration of characteristics. Therefore, semiconductors 5 and 7 are SixC _1-X (0
<x<1) to improve reliability.

That is, the electrode 3 whose main component is tin oxide, P type
SixC _1-X 0<x<1
0.1~3μ e.g. 0.5μ) - N-type Si (500A~1μ e.g.
0.2μ) N type SixC _1-X (0<x<1x=0.9) (100~500
The electrode 2 has a structure in which the main component is ITO (for example, 200 Å). By creating a heterojunction in this energy band, it was possible to prevent the generation of insulating silicon oxide at the interface between the electrode and the semiconductor at high temperatures of 150 to 300 degrees Celsius, resulting in high reliability. .

Example 1 This example, whose outline is shown in Fig. 4, uses an optical readout method that allows photoelectric program rewriting.
ROM is non-volatile memory. This optical memory is extremely effective when used as an optical memory disk for office automation and can be programmed and used as desired.

That is, in FIG. 4, A indicates memory writing, and B indicates reading. Glass in the drawing,
Insulating substrate 4 (100
A first conductivity type electrode 3 of 0.5 to 1 .mu. thick was formed on the substrate by a reflective electrode (for example, aluminum) 9 and CTO (for example, tin oxide) 8. Further, on top of this, a PIN junction as described above is provided, and oxygen, hydrogen and Na, K, P, N are present in the I layer.
At least one of the silicon-based non-single crystal semiconductors 1 doped with 1 x 10 ¹⁶ to 1 x 10 ²¹ cm ^-3 , for example, N- x 10 ¹⁹ and N x 10 ²⁰ cm ^-3 , has a thickness of 0.7μ. formed to a thickness. Further above it is ITO's CTO2
was formed on the entire surface. This board has a disc shape similar to a record board. The address was controlled by a microcomputer 32, and a nitrogen laser beam 35 (emission wavelength: 337 nm) was irradiated from a light source 35 with a beam diameter of 1 to 100 μφ, for example, 5 μφ. 100 to 2000 of such short wavelength ultraviolet light of 500 nm or less
By applying at an intensity of mW/cm ² , recombination centers were generated and the electrical conductivity was “0” in FIG. Thus, for example, "0" in 24, 26
I wrote. As a result, the other address 25 is "1"
It became.

To write this memory, the entire board is irradiated with an ultra-high pressure mercury lamp (2537 Å) to make it insulated to "0".
Conversely, a specific area may be set to "1" by irradiating 10.6μ far infrared light with a CO laser (waveguide type).

This method has the feature that it is possible to improve the noise margin during reading.

Memory reading is shown in Figure 4B, where a weak (strong within the range where the stored information does not change) light irradiation is applied to a predetermined address using an argon laser (488 nm, 515 nm).
33 was specified by irradiating the address to be read.
The address was input into the computer 32, and an electric pulse 29 was applied in synchronization with the signal. Then, the information of the detection address irradiated with light is detected 31 by the resistor 26.

This time chart is shown in FIG.

That is, FIGS. 5A and 5B are the memory writing.

High resistance regions 44 and 46 are selectively formed in a part of the optical disk by intense light pulse irradiation 47 and 48 in FIG. 5B.
It is formed as follows. 44, 45, and 46 correspond to 24, 25, and 26 in FIG. 4A.

Furthermore, as shown in FIGS. 5C and 5D, a voltage 29 was applied in synchronization with the light, and the output potentials were obtained as 38 and 39 as shown in FIG. 5D.

In other words, this optical memory (program ROM) uses light to make a part of a record-like disk a high resistance area or a low resistance area, and conversely makes the other part a relatively low resistance area or a high resistance area. Address designation is performed using light without contact, and readout is conducted through electrical conduction, making contactless high-electricity readout possible. For this reason, we were able to create a rewritable ROM with so-called photoelectric writing. The present invention differs in principle from the conventionally known non-rewritable optical disk memory which is formed by selectively removing a portion of a substrate. Furthermore, it has been found that the stored information can be rewritten and is nonvolatile, making it ideal as a large-capacity optical disk memory.

As is clear from the above explanation, the present invention creates a non-volatile memory by adding a large amount of impurities such as hydrogen and oxygen to amorphous silicon and controlling the reversible change in electrical conductivity. Providing this PN junction in a semiconductor is an embodiment of this, and its "0" is not just one PN junction, but a PNIPN junction, etc.
Increasing the contrast of "1" is also effective, and many applications based on the same technical idea are possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor device using the PIN junction of the present invention. FIG. 2 is an energy band diagram for explaining the theory of the present invention. FIG. 3 shows the change characteristics of electrical conductivity of a non-single crystal semiconductor. Fourth
The figure shows an embodiment of a semiconductor memory device of the present invention.
FIG. 5 shows a time chart used in the embodiment of FIG.

Claims (1)

[Scope of Claims] 1. Silicon to which hydrogen and oxygen are added, or a non-single crystal semiconductor mainly composed of silicon, on a first electrode consisting of a conductive layer on a conductive substrate or an insulating substrate; A second electrode is provided on a single crystal semiconductor, and at least one of the first and second electrodes is transparent. means for forming a region, means for locally or partially irradiating infrared rays or thermal energy to form a high electrically conductive region, and a first or second electrode in the low electrically conductive region and the high electrically conductive region. 1. An optical memory device comprising means for emitting light from the side and detecting the degree of electrical conduction at an address irradiated with light. 2. In claim 1, the non-single crystal semiconductor contains impurities selected from groups of the periodic table such as Na, K, P, N, etc. in an amount of 5×10 ¹⁶ to 1×10 ²¹
An optical memory device characterized by being doped with cm ^-3 . 3. An optical memory device according to claim 1, characterized in that a low electrical conductivity region is formed by applying a reverse bias to a non-single crystal semiconductor having a PIN junction and irradiating it with a light beam. 4 A first electrode consisting of a conductive layer on a conductive substrate or an insulating substrate, silicon to which hydrogen and oxygen are added, or a non-single crystal semiconductor mainly composed of silicon, and a second electrode on the non-single crystal semiconductor. a non-volatile optical memory having a second electrode, at least one of the first or second electrode being translucent, and forming a low electrical conductivity region in the semiconductor by locally irradiating the optical memory with a light beam; forming a high electrically conductive region by locally or partially irradiating the semiconductor with infrared rays or thermal energy; 1. An optical memory device write/read method comprising a step of reading out stored memory information by irradiating light from the second electrode side and detecting the level of electrical conduction at an address irradiated with light. 5 In claim 4, the non-single crystal semiconductor contains impurities selected from groups of the periodic table such as Na, K, P, N, etc. in an amount of 5×10 ¹⁶ to 1×10 ²¹
An optical memory device write/read method characterized by cm ^-3 doping. 6. An optical memory device read/write method according to claim 4, characterized in that a low electrical conductivity region is formed by irradiating a non-single crystal semiconductor having a PIN junction with a light beam while applying a reverse bias. .