JPH08255843A - Semiconductor rom device and method of writing data therein - Google Patents

Abstract

PURPOSE: To lessen a time necessary for writing data in a semiconductor ROM device for delivery as a product by a method wherein the cross points of a cross point cell structure are connected with amorphous silicon, and the wiring is selectively spot-irradiated with an ultraviolet laser beam according to data patterns. CONSTITUTION: A word line L1 and data lines DA1 , DA2 , DA3 , ... are connected together at the cross points of them through a-Si wirings 511 , 512 , 513 , .... When data are written in this semiconductor ROM device of cross point cell structure, the a-Si wirings 511 , 512 , 513 , ... are selectively spot-irradiated with ultraviolet laser rays corresponding to a data pattern. a-Si is turned crystalline or into a poly-Si structure by irradiation with ultraviolet laser rays, so that the a-Si wirings 511 , 512 , 513 , ... are lessened enough in load resistance to become electrically conductive, and data are capable of being written in this semiconductor ROM device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor ROM device having a cross-point cell structure and a data writing method for the semiconductor ROM device.

[0002]

2. Description of the Related Art A table used for executing a non-linear operation such as a γ correction of a television is stored in a ROM having a relatively small capacity, and this ROM has, for example, a cross point cell structure. Semiconductor ROM
The device is used. In this semiconductor ROM device having a cross-point cell structure, the cross points of wirings arranged in the vertical and horizontal directions, that is, the two-dimensional XY directions are respectively MOS (metal oxide).
semiconductor) transistor is connected.

FIG. 6 shows a schematic structure of a semiconductor ROM device having a cross-point cell structure, which will be described below.

The vertical (Y direction) wiring is a so-called data line, and these data lines DA ₁ , DA ₂ , DA ₃ , ...
The reset transistor _{M 1, M 2, M 3} , through ... is grounded, for these reset transistors _{M 1, M 2, M 3} , to the gates of ..., output data A reset pulse signal for timing the operation is input. The horizontal (X direction) wiring is a so-called word line, and the input signals from the input terminals I ₁ , I ₂ , ..., I _n are input to the X decoder 1 and decoded by the X decoder 1. By doing so, the word lines L ₁ , L ₂ ,
..., one of the word line L is selected from among the L _n, the power supply voltage V _CC to the selected word line L is applied.

A cross point between the data line DA and the word line L is connected by a transistor T. Specifically, the word line L ₁ and the data lines DA ₁ , DA ₂ , DA ₃ , ...
・ The cross points with and are the transistors T ₁₁ , T ₁₂ , T ₁₃ ,.
··· Connected by word line L ₂ and data line DA ₁ ,
The cross point with DA ₂ , DA ₃ , ... is the transistor T
_The word line L is connected by ₂₁ , T ₂₂ , T ₂₃ , ...
Cross points between _n and the data lines DA ₁ , DA ₂ , DA ₃ , ... _Are connected by transistors T _n1 , T _n2 , T _n3 ,. The gates of these transistors T are connected to the grounded gate line GL and are set to the ground potential.

The plurality of transistors T are a depletion type transistor indicated by D, which is always on, or an enhancement type transistor indicated by E, which is normally off and is turned on by applying a voltage. It shows that the data has been written.

That is, in order to write data such as a program in a semiconductor ROM device having a cross-point cell structure, an ion implantation mask corresponding to the data pattern is used,
Impurity ions are implanted only into the channel portion of a specific transistor. As a result, the transistor T is changed from the enhancement type to the depletion type, and the gate of the transistor becomes conductive even at the ground potential. In this way, a data pattern is written in a memory cell array in which a plurality of memory cells are regularly arranged in a so-called matrix. Here, the data pattern indicates a two-dimensional pattern on a matrix of cells and also indicates a bit pattern.

After the ion implantation step, a wiring step, a passivation film forming step, and the like are performed to manufacture a mask ROM as a product.

Next, the operation of the semiconductor ROM device having the cross-point cell structure will be described with reference to the data input / output timing chart shown in FIG.

Specifically, in FIG. 7, data output and reset pulse signals on the data lines DA ₁ , DA ₂ and DA ₃ in the Y direction when the word line L ₁ which is the wiring in the X direction is selected. The output timing of is shown.

In an actual operation, the word line L ₁ shown in A of FIG. 7 is selected at time t ₁ , the power supply voltage V _CC is applied to this word line L ₁ , and the word line L ₁ becomes High (1).
It becomes the state of. Before the power supply voltage V _CC is applied to the word line L ₁ , the reset pulse signal shown in B of FIG. 7 is applied to the data lines DA ₁ , DA ₂ , DA ₃ and all the data lines DA ₁ , DA ₂ and DA ₃ are reset to the ground potential, that is, the state of Low (0) by the reset transistors M ₁ , M ₂ and M ₃ .

When the word line L ₁ becomes HIgh (1), the data line DA ₁ becomes conductive because the transistor T _{11 at} the crossing point with the word line L ₁ is a depletion type, and the data line DA ₁ is removed from the word line L _1. A current flows, and the word line L ₁ becomes High (1) at time t _{1 as} shown in FIG. 7C. On the other hand, the data line DA ₂ is in a non-conducting state because the transistor T _{12 at} the crossing point with the word line L ₁ is an enhancement type, and no current flows from the word line L ₁ .
Therefore, the data line DA ₂ is Lo as shown in D of FIG.
It remains in the w (0) state. Similarly to the data line DA ₁ , the data line DA ₃ changes to the High (1) state at time t _{1 as} shown in E of FIG.

Such data lines DA ₁ , DA ₂ , DA ₃
From the X decoder 1 shown in FIG. 6 as output data corresponding to the input data from the data output device 2 as a binary data string of 1s or 0s.

[0014]

By the way, in the semiconductor ROM device having the above-mentioned cross-point cell structure,
It takes about two months to turn around time (TAT), which is a period from receiving an order for data, writing a pattern according to this data into a semiconductor ROM device, and delivering it as a product, so the write data is changed for each television model. And then difficult to produce.

In view of the above situation, the present invention provides a semiconductor ROM device and a data writing method for the semiconductor ROM device, which can shorten the period from the writing of data to the product.

[0016]

Means for Solving the Problems A semiconductor RO according to the present invention
In the M device, the cross points are connected by the wiring made of amorphous silicon, and the data is written by selectively irradiating the wiring with spots of the ultraviolet laser light according to the data pattern. Solve the problem.

Further, according to the data writing method of the semiconductor ROM device of the present invention, the wiring made of amorphous silicon, which connects the cross points of the wirings arranged two-dimensionally, is exposed to ultraviolet rays according to the data pattern. The above-mentioned problems are solved by selectively irradiating a spot of laser light to write data.

[0018]

In the present invention, the cross points of the cross-point cell structure are connected by the wiring made of amorphous silicon, and this wiring is selectively spot-irradiated with the ultraviolet laser light according to the data pattern. Since it is a semiconductor ROM device in which data is written, it can be manufactured as a product in a short period of time.

Further, the wiring composed of amorphous silicon at the cross points of the cross point cell structure is selectively spot-irradiated with an ultraviolet laser beam according to the data pattern to write the data to the semiconductor ROM device. Therefore, the resistance value of the wiring is reduced by crystallization of the amorphous silicon, and the wiring is brought into a conductive state to write data.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a semiconductor ROM device according to the present invention.

The semiconductor ROM device shown in FIG. 1 has a cross point cell structure constituted by connecting cross points of wirings arranged two-dimensionally, and the cross points are made of amorphous silicon. The data is written by connecting the wirings with the wirings and selectively irradiating the wirings with ultraviolet laser light in accordance with the pattern of the data.

The vertical (Y direction) wiring is a so-called data line, and these data lines DA ₁ , DA ₂ , DA ₃ ,.
..., the reset transistor _{M 1, M 2, M 3} , ··
A reset pulse signal for timing the output of data is input to the gates of these reset transistors M ₁ , M ₂ , M ₃ , ... The horizontal (X direction) wiring is a so-called word line, and the input signals from the input terminals I ₁ , I ₂ , ..., I _n are input to the X decoder 1 and decoded by the X decoder 1. The word line L ₁ ,
One word line L is selected from L ₂ , ..., L _n , and the power supply voltage V _CC is applied to the selected word line L. The data line DA and the word line L are made of polysilicon (hereinafter Pol), which is polycrystalline silicon, as described later.
It is made of a metal material such as y-Si) or aluminum.

The cross point between the data line DA and the word line L is an a-Si wiring 5 made of amorphous silicon (hereinafter referred to as a-Si) which is amorphous silicon.
Is connected by. Specifically, the cross point between the word line L ₁ and the data lines DA ₁ , DA ₂ , DA ₃ , ... Is a
-Si wirings 5 ₁₁ , 5 ₁₂ , 5 ₁₃ , ... Are connected, and the word line L ₂ and the data lines DA ₁ , DA ₂ , DA ₃ ,.
・ The cross points with and are the a-Si wiring 5 ₂₁ , 5 ₂₂ , 5 ₂₃ , ・
.. are connected by a word line L _n and a data line DA ₁ ,
The cross point with DA ₂ , DA ₃ , ... Is the a-Si wiring 5
It is connected by _n1 , 5 _n2 , 5 _n3 , ....

First, in the initial state, since the load resistance value of the a-Si wiring 5 is very high, an arbitrary word line L in the X direction is formed.
Even if is selected to be in the High (1) state, no current flows from the word line L to the cross point, and all data output from the data output device 2 in the Y direction becomes Low (0).

This cross-point cell structure semiconductor R
To write data in the OM device, the a-Si wiring 5 is selectively spot-irradiated with the ultraviolet laser light according to the pattern corresponding to the data. Crystallization of a-Si by irradiation with ultraviolet laser light causes a-Si to be Poly-
In place of the Si structure, the load resistance value of the a-Si wiring 5 becomes sufficiently small, and the a-Si wiring 5 becomes conductive and the data is written.

In this way, a by irradiation with ultraviolet laser light
Data is written by utilizing a change in resistance value due to crystallization of -Si.

[0027] Note that in a-Si wiring 5 _11, 5 _12, 5 ₁₃ among a plurality of a-Si wiring 5 shown in FIG. 1, specifically, a-Si wiring ultraviolet laser light is not irradiated 5
For ₁₂ indicated by a-Si, a-Si wiring 5 ₁₁ UV laser light changes is irradiated to Poly-Si structure,
5 ₁₃ is indicated by p-Si.

Next, FIG. 2 shows a schematic structure of an ultraviolet laser light spot irradiation device as a data writing device for writing data in the semiconductor ROM device having the above-mentioned crosspoint cell structure.

The ultraviolet laser beam spot irradiation apparatus shown in FIG. 2 includes a laser light source 1 for emitting an ultraviolet laser beam, an electronic shutter 2 for controlling the on / off of the ultraviolet laser beam, and a condensing optical system for concentrating the ultraviolet laser beam. 4, an XY stage 6 that moves in two-dimensional directions, a CCD camera 8 that captures the reflected light of the emitted ultraviolet laser light, a monitor 9 that displays the captured image, and the XY stage 6 and the monitor 9 described above. It is composed of a control device 7 for controlling. A pattern according to data is written by scanning and selectively irradiating an a-Si wiring of a semiconductor ROM device with a spot of an ultraviolet laser beam by the ultraviolet laser light spot irradiating device.

In this ultraviolet laser beam spot irradiation device, the control device 7 including a computer or the like controls the
Ultraviolet laser light, so-called UV laser light, is emitted from the laser light source 1. As the ultraviolet laser light, for example, far ultraviolet laser light using the fourth harmonic of Nd: YAG laser capable of continuous oscillation is used.

FIG. 3 shows a specific structure of the laser light source 1 for emitting the ultraviolet laser light, that is, the ultraviolet laser light source.

In this ultraviolet laser light source, a semiconductor laser element such as a laser diode (not shown) is used as an excitation light source element, and the excitation laser light having a wavelength of 808 nm from this semiconductor laser element is a quarter wavelength plate ( QW
From the incident surface of P) 31, it is incident on the laser medium 32 using Nd: YAG, for example.

Here, the incident surface of the quarter-wave plate 31 has a wavelength selectivity such that the excitation laser light is transmitted and the fundamental wave laser light having a wavelength of 1064 nm generated in the laser medium 32 is reflected. A so-called dichroic mirror having a reflecting surface is formed.

The wavelength 106 generated by the laser medium 32
The output of the 4 nm fundamental-wave laser light is adjusted by the filter 33 and is reflected by the folding mirror 35.
By being incident on the nonlinear optical crystal element 37 made of, for example, KTP via the output coupler 36,
Harmonic generation (SHG) is performed. The second harmonic laser light having a wavelength of 532 nm generated by the second harmonic generation is reflected by the mirror 40 and then by the mirror 38.

The laser light reflected by the mirror 38 is
It is incident on the optical isolator 41 via the lens 39.

The optical isolator 41 is for avoiding returning of the incident second harmonic laser light to the laser element. The second harmonic laser light that has passed through the optical isolator 41 is incident on an electro-optical phase modulator (EOM) 42 and is subjected to phase modulation. That is, the phase modulation of the output far-ultraviolet laser light is performed. The phase-modulated second harmonic laser light is incident on the external resonator 50.

The external resonator 50 is used as a reflecting means.
It is configured by including a concave mirror 51, an output coupler 52, and reflection mirrors 54 and 55. Also,
In the optical path of the external resonator 50, a wavelength conversion element 53 made of a nonlinear optical crystal such as BBO is arranged.
As a result, fourth harmonic generation is performed in the external resonator 50, and far-ultraviolet laser light having a wavelength of 266 nm is generated.

Further, in this external resonator 50, a voice coil motor (VCM) is used for positioning the upper concave mirror 51, and the VCM controls the movement of the position of the concave mirror 51, whereby external resonance is achieved. Bowl 5
The optical path length within 0 can be minutely changed.

Specifically, the second harmonic laser light incident on the concave mirror 51 is sent to the photodetector 44 and detected. The detection signal from the photodetector 44 is sent to the locking circuit 45, and the locking circuit 45 causes the VCM to operate.
Is controlled to control the position of the concave mirror 51.

As a result, the resonance frequency of the external resonator 50 is controlled, the second harmonic laser light can be efficiently drawn into the external resonator 50, and the far-ultraviolet laser light can be stably generated. Further, in the locking circuit 45,
It also controls the phase modulation of the electro-optic phase modulator 42.

The ultraviolet laser light emitted from the laser light source 1 is a laser light capable of continuous oscillation, and this continuous oscillation ultraviolet laser light is acousto-optic modulation (AOM).
The high-speed electronic shutter 2 using elements etc.
The semiconductor chip 5 which is a semiconductor ROM device on the Y stage 6 is on / off controlled so as to be spot-irradiated. The ultraviolet laser light controlled by the electronic shutter 2 is reflected by a mirror 3 and a diameter of 1 μm on a semiconductor chip 5 by a condensing optical system 4 including an objective (condensing) lens and the like.
It is focused on a spot size of about m.

The semiconductor chip 5 is mounted on an XY stage 6 whose movement is precisely controlled.
The stage 6 is two-dimensionally driven and controlled by a control device 7 using a computer or the like. As a result, the XY stage 6 is driven to a position where a light spot is focused on a desired memory cell, that is, an a-Si wiring.

Further, the control device 7 controls the output of the ultraviolet laser light emitted from the laser light source 1, and the controlled ultraviolet laser light has a desired a-
The electronic shutter 2 is opened and closed so that the Si wiring is irradiated. Data is written by repeatedly performing such a work operation.

Here, the structure of the memory cell will be described with reference to FIGS.

FIG. 3 shows a plan view of the memory cell and FIG.
[Fig. 3] is a cross-sectional structural view of a memory cell.

In FIGS. 3 and 4, the word line L in the X direction is shown by the Al wiring 4 made of aluminum (Al), and the data line DA in the Y direction is Poly.
This is shown by the Poly-Si wiring 3 made of -Si. The cross point between the Al wiring 4 and the Poly-Si wiring 3 is, as shown in FIG. 4, the Al wiring 4 and the Poly-S wiring.
The wiring is connected by the a-Si wiring 5 which is in contact with the i wiring 3. Here, the contact between the Al wiring 4 and the a-Si wiring 5 so-called contact is made by the contact layer C ₁ , and P
The contact between the poly-Si wiring 3 and the a-Si wiring 5 is made by the contact layer C ₂ .

Specifically, as shown in FIG. 5, on the insulating film 7 made of SiO ₂ on the Si substrate 6, Poly-Si is formed.
The wiring 3 and the Al wiring 4 are formed, and this Poly-Si is formed.
The Poly-Si wiring 3 is provided between the wiring 3 and the Al wiring 4.
And the a-Si wiring 5 is formed in contact with the Al wiring 4. Then, the area shown by the laser light irradiation area LA in FIG. 4 is irradiated with the ultraviolet laser light.

A passivation film 8 made of SiO ₂ and having a high transmittance for ultraviolet laser light is formed on the Al wiring 4 with a film thickness of about 2 μm, and the ultraviolet laser light passes through the passivation film 8. Through a-Si wiring 5
Irradiated on.

Further, the a-Si wiring 5 is preferably arranged so as to be as thin and long as possible in order to secure a sufficient resistance value and to secure a wide area irradiated with the ultraviolet laser light.

The degree of change in the resistance value of the a-Si wiring 5 depends on the material characteristics of the a-Si, particularly the doping amount of impurities such as phosphorus and arsenic. Appropriate conditions should be applied. For example, it is possible to change the resistance value by 3 to 4 digits.

In this way, the semiconductor chip 25, which is a semiconductor ROM device having a cross-point cell structure, is scanned with the light spot of the focused laser beam, and the a-Si wiring 5 corresponding to the desired data pattern is obtained. The data is written by selectively irradiating the.

The data input / output operation in the semiconductor ROM device in which the data is written is carried out in substantially the same manner as the data input / output operation in the conventional semiconductor ROM device having the cross-point cell structure using transistors.

Specifically, as shown in FIG. 1, a-Si is Po.
a-Si wiring at the cross point changed to the ly-Si structure 5 ₁₂
Since the resistance value is sufficiently low and is close to the conductive state, for example, when a current flows from the selected X-direction word line L ₁ to the a-Si wiring 5 ₁₂ , it corresponds to this a-Si wiring 5 ₁₂ . The output from the data line DA _{2 in the} Y direction is High.
It becomes (1). On the other hand, cross-point a-Si wirings 5 ₁₁ , 5
_{Since 13} remains a-Si, a sufficient current does not flow at these cross points, and the corresponding data line DA in the Y direction is
The output from ₁ and DA ₃ becomes Low (0). Thus, for any data input from the X decoder 1, Y
The data output from the directional data line DA can be taken out as a binary data string of 1 or 0.

The objective lens of the condensing optical system 4 is
The chromatic aberration is corrected over a wide wavelength range from the ultraviolet range to the visible range, and the reflected light of the light spot irradiated on the semiconductor chip 5 is written during the data writing operation.
The image pickup element of the CCD camera 8 so-called C via the mirror 3.
It is adjusted to form an image on the DD. The image signal of the data writing state obtained by this CCD camera 8 is
It is sent to a monitor 9 such as a television. This monitor 9 is controlled by the control device 7, and C
By displaying an image from the image signal from the CD camera 8, the writing state of data can be observed.

In the above embodiment, the case where the ultraviolet laser light by the fourth harmonic of the semiconductor laser is used as the ultraviolet laser light used for writing the data is explained, but the ultraviolet laser light is continuous oscillation. As long as it is an ultraviolet laser beam, it is possible to use a laser light source other than a semiconductor laser.

[0056]

As is apparent from the above description, in the semiconductor ROM device according to the present invention, the cross points are connected by the wiring made of amorphous silicon, and the ultraviolet laser is connected to this wiring according to the data pattern. Since the data is written by selectively irradiating light with a spot, it is structurally simpler than the conventional semiconductor ROM device and can be easily manufactured. Therefore, the manufacturing cost can be reduced and the TAT can be reduced. It is effective for shortening. Further, by writing a microcode in the semiconductor ROM device, the semiconductor R
By incorporating the OM device into an electronic information device such as a personal computer or an engineering workstation (EWS), and by making each electronic information device an individual identification number, management of these electronic information devices on the network is facilitated. Therefore, it can be effectively used to prevent unauthorized network operations and theft of electronic information devices.

Further, in the data writing method of the semiconductor ROM device according to the present invention, the wiring made of amorphous silicon, which connects the cross points of the wirings arranged two-dimensionally, is irradiated with ultraviolet rays according to the data pattern. Data can be written by selectively irradiating the laser beam to write data, by lowering the resistance value of the wiring due to crystallization of amorphous silicon, and by making the wiring conductive. Data can be written to the packaged semiconductor ROM device. Specifically, the semiconductor RO before data writing is initialized in the form of a package.
A large amount of M chips are prepared, and for example, a semiconductor ROM device is manufactured by changing the data in the γ correction table for each model of television and writing the data to manufacture a semiconductor ROM device. It can be carried out.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor ROM device according to the present invention.

FIG. 2 is a schematic configuration diagram of an ultraviolet laser light spot irradiation device.

FIG. 3 is a schematic configuration diagram of an ultraviolet laser light source.

FIG. 4 is a schematic plan view of a memory cell.

FIG. 5 is a schematic cross-sectional structure diagram of a memory cell.

FIG. 6 is a schematic configuration diagram of a conventional semiconductor ROM device.

FIG. 7 is a timing chart of data input / output.

[Explanation of symbols]

 1 X Decoder 2 Data Output Device 3 Poly-Si Wiring 4 Al Wiring 5 a-Si Wiring 6 Si Substrate 7 Insulating Film 8 Passivation Film 21 Laser Light Source 22 Electronic Shutter 24 Condensing Optical System 25 Semiconductor Chip 26 XY Stage 27 Control Device 28 CCD camera 29 monitor

Claims (2)

[Claims] 1. A semiconductor ROM device having a cross-point cell structure configured by connecting cross points of wirings arranged two-dimensionally, wherein the cross points are connected by wiring made of amorphous silicon. Data is written by selectively irradiating the wiring with spots of ultraviolet laser light according to a data pattern.
OM device. 2. Writing data by selectively irradiating spots of an ultraviolet laser beam on a wiring made of amorphous silicon, which connects cross points of wirings arranged two-dimensionally, according to a data pattern. A method for writing data in a semiconductor ROM device, comprising: