JPS6146045A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain in program element-foming technique replaceable with a fuse while preventing the damage of a semiconductor integrated circuit due to moisture instruding into a package by short-circuiting a gate electrode and a substrate through the irradiation of a laser to a gate electrode section. CONSTITUTION:When a laser is projected toward a gate electrode 4 from the upper section of a passivation film 3, the gate electrode 4 consisting of a polysilicon layer is melted. The melted electrode material penetrates a gate insulating film 6 and reaches the main surface of a semiconductor substrate 5, and the gate electrode 4 and the substrate 5 are short-circuited. Since the gate insulating film 6 in a MOSFET is extremely thin at the time, the gate insulating film 6 is broken simply when the gate electrode 4 is melted by the laser, thus shoft-circuiting the gate electrode and the substrate. According to such a method, a process in which an opening section is formed to the passivation film 3 on the gate electrode 4 for the MOSFET as a program element is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to semiconductor technology and further to program element technology, and relates to a technology that is effective when used, for example, to form a program element that can replace a fuse in a semiconductor device.

[Background Art] In a large-capacity semiconductor storage device such as a 256 kilobit dynamic RAM (random access memory), a memory column containing a defective bit in a memory array is switched with a pre-if memory column. Redundant circuits are sometimes provided for the purpose of improving chip yield.

In order to switch to this redundant circuit, conventionally, a fuse made of polysilicon or the like is generally formed on the semiconductor substrate via an insulating film such as a silicon oxide film, and switching is performed depending on whether or not this fuse is blown. There is. In this case, the fuse can be blown by applying a voltage of about 20V across both ends to cause an overcurrent to flow, or by irradiating it with a laser. For example, as shown in Japanese Patent Application No. 58-219408)
.

However, as mentioned above, in a semiconductor device using a polysilicon fuse as a program element.

When blowing a fuse, the passivation film above the cut part is placed so that the components of the fuse that are evaporated can be scattered outside, and in order to prevent the passivation film from being damaged by the laser since a high-energy laser is used in laser blowing. A portion of the fuse is removed to form an opening (window). Therefore, if this opening is left as it is after the fuse has blown, moisture will adhere there, and that moisture will also enter the area between the eyebrows. There is a risk that it will penetrate under the insulating film and deteriorate the elements that make up the semiconductor integrated circuit.

Particularly in plastic packages that have recently come into use, it is relatively easy for moisture to infiltrate into the package, so if there is an opening in the passivation film where the fuse is formed, damage may easily occur due to moisture intrusion. There is a point.

Furthermore, in order to prevent damage due to moisture, a protective film is formed over the opening after blowing out the fuse, but this method has the disadvantage of increasing the number of process steps.

[Object of the Invention] An object of the present invention is to provide a programming element formation technique that can replace fuses in semiconductor integrated circuits.

Another object of the present invention is to provide a programming element forming technique that can prevent damage to a semiconductor integrated circuit due to moisture intruding into a package without complicating the process.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of Ming] The outline of typical inventions disclosed in this application is as follows.

That is, MOSFET (
Using a MOSFET (insulated gate field effect transistor), a relatively low-energy laser beam is irradiated onto the gate electrode of the MOSFET from above the passivation film to destroy the gate and create a short circuit between the gate and the substrate. Programming can be performed using a low-energy laser without forming openings in the passivation film of the element formation area that allow moisture to enter. This eliminates damage to integrated circuits caused by moisture without complicating the process. The object of the present invention is to provide a programming element that can prevent the above problems.

[Embodiment 1] FIG. 1 shows an embodiment in which the present invention is applied to a program element for redundant circuit switching in a CMO8 (complementary MOS) type RAM.

In this example, a MOSFET as a programming element
A programmable level setting circuit 1 is provided by a MOSFET QP and a high resistance element R connected between the gate terminal of the MOSFET QP and the ground point of the circuit. Above M
Power supply voltage Vcc is applied to the base of O5FETQP,
Power supply voltage Vcc is also applied to the source terminal and drain terminal of MOSFETQP. Although not particularly limited, the MOSFETQP shown in FIG. 2(A) 4. : As shown, the high resistance element R is formed in a P channel shape,
It is composed of a non-doped polysilicon layer formed so as not to contain impurities.

The potential of the output node n of the level setting circuit 1 is, for example, the column selection signal φy output from the Y decoder 2.
P-channel type MO5FETQI and N-channel type MO5FE as transfer gates that selectively transfer
It is applied to the gate terminal of TQ2. The level setting circuit 1 is provided corresponding to each memory column in a memory array (not shown).

The MO3FETQp that constitutes the level setting circuit 1 is as follows:
As shown in FIG. 2A, when a laser is irradiated from above the passivation film 3 toward the gate electrode 4, the gate electrode 4 made of a polysilicon layer is melted.

Then, this melted electrode material penetrates through the gate insulating film 6 and reaches the main surface of the semiconductor substrate 5, as shown in FIG. In this case, since the gate insulating film 6 of the MOSFET QP is very thin, it is easily destroyed when the gate electrode 4 is melted by the laser, resulting in a short circuit between the gate electrode and the substrate.

Furthermore, according to this embodiment, unlike conventional polysilicon fuses, it is not necessary to completely blow out the fuse, but it is sufficient to simply melt it, so that a low-energy laser can be used. Therefore, as in the above example,
Even if the passivation film 3 formed on the gate electrode 4 is irradiated with laser from above to melt the gate electrode 4, the passivation film 3 is hardly damaged.

Therefore, according to this embodiment, an opening is formed in the passivation film 3 on the gate electrode 4 of the MOSFET Qp as a programming element, or after the gate and the substrate are short-circuited by laser irradiation, the passivation film 3 is
There is no need to take a process that involves the formation of .

As described above, MOSFE as a program element
When the gate insulating film 6 of the TQP is broken and the gate electrode 4 and the substrate 5 are short-circuited, the power supply voltage Vcc is applied as the substrate voltage to the N-type semiconductor substrate 5, so that the voltage as shown in FIG. Output node n1 of level setting circuit 1 is set to a high level close to power supply voltage Vcc. The potential of the output node n1 causes the P-channel type MOSFET Qx as a transfer gate to be rendered non-conductive, and the N-channel type MOSFET Q2 to be rendered conductive. Then, the column selection signal φy output from the Y decoder 2 is not transmitted to the column switch that connects the data line of the regular memory column in the memory array to the main amplifier, but is sent to the redundant column switch that selects the spare memory column. be able to communicate to

On the other hand, when the gate electrode 4 of the MOSFET QP in the level setting circuit 1 is not irradiated with the laser, the MOSFET
Since the gate insulating film 6 of the ETQP is not destroyed, the gate electrode 4 and the substrate 5 are insulated. Therefore, the potential of the output node n1 of the level setting circuit l is set to a low level similar to the ground potential supplied through the high resistance element R.

This allows MO3FE to function as a transfer gate.
TQ1 is made conductive and MO8FETQ2 is made non-conductive. As a result, the column selection signal φy output from the Y decoder 2 is transmitted to the column switch that selects the regular memory column, and the spare memory is not selected.

Therefore, among the level setting circuits i provided corresponding to each regular row in the memory array, the MOSFET QP in the level setting circuit 1 corresponding to the memory row containing the defective bit found by the inspection is However, if the gate and substrate are short-circuited by irradiation with a laser, a spare memory column can be selected in place of the memory column containing the defective bit.

In addition, in the above embodiment, M as a program element
The OSFETQP can be formed at the same time as the P-channel MOSFET that constitutes the memory cell or its peripheral circuit. Furthermore, in a static RAM consisting of a flip-flop type memory cell, the high resistance element R constituting the level setting circuit 1 can be formed at the same time as the load resistor consisting of a polysilicon layer in the memory cell.

Embodiment 2] FIG. 3 shows an embodiment in which the present invention is applied to a level setting circuit for redundant circuit switching in a RAM consisting only of N-channel MO8FETs.

In this example, N is used as a programming element whose source and drain terminals and substrate are connected to the circuit ground point.
A level setting circuit 1 is constituted by a channel type MO5FET Qp'' and a high resistance element R connected between one gate terminal and a power supply voltage Vcc.

The MO3FETQp' is formed directly on the main surface of a P-type semiconductor substrate, and by biasing the semiconductor substrate to a ground potential, a ground potential is applied to the base of the MO5FETQp'.

Therefore, in the level setting circuit 1 of this embodiment, the MOSFET
When the gate electrode of ETQp' is irradiated with a laser and the gate electrode and the substrate are short-circuited, the output node n1' is brought to a low level close to the ground potential. On the other hand, if the laser is not irradiated, the gate of MOSFET Qp' will not be destroyed, so the output node n1 is set to a high level such as the power supply voltage Vcc.

Therefore, the potential of the output node n1' of the level setting circuit 1 is received by the inverter 7 whose threshold voltage is a voltage between the above two levels, and the output of the inverter is output from the Y decoder 2. The redundant circuit can be switched by controlling the opening and closing of the transfer gates that transmit the column selection signal φy to the column switches of the regular memory column or the spare memory column.

The level setting circuit of this embodiment can be applied to a RAM having an 0MO8 configuration, when an N-channel MO8FET formed on a P-well region is used as a program element.

In that case, the base of MO5FETQp' is not an n-type semiconductor substrate but a P well region.

Note that in the above embodiment, a MOS as a program element is used.
Although it is assumed that the gate electrode of FETQp is formed of a polysilicon layer, it is not limited to this, but the gate electrode may be made of aluminum or other metals, silicon compounds of these, or a composite structure (multilayer structure) thereof. It can also be applied to

Further, in the above embodiment, the laser is irradiated from above the passivation film 3 toward the gate electrode 4, but it goes without saying that there may be an insulating film between the eyebrows between the passivation film 3 and the gate electrode 4. do not have.

[Effects] (1) A MOSFET (insulated gate field effect transistor) is used instead of a fuse as a programming element for switching redundant circuits in a semiconductor memory device, and a relatively low voltage Programming is performed by irradiating a high-energy laser to destroy the gate and create a short-circuit state, thereby eliminating the need to form an opening that would be an entry point for moisture, etc. in the passivation film of the main element forming part of the progera. The ability to program with a low-energy laser has the effect of preventing moisture damage to integrated circuits without complicating the process.

(2) A MOSFET (insulated gate field effect transistor) is used instead of a fuse as a programming element for redundant circuit switching in a semiconductor memory device, and a relatively low energy laser is applied to the gate electrode of the MOSFET from above the passivation film. irradiation to destroy the gate and short circuit between the gate and the substrate II! ! When used in MO8 integrated circuits, the program element can be formed at the same time as the circuit elements, making it possible to replace fuses without changing the process at all. This has the advantage that a program element can be formed.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, in the above embodiment, the gate electrode and the substrate of the MOSFET QP as a programming element are short-circuited by laser irradiation, but the short-circuit is not limited to this. It is also possible. Further, the configuration of the redundant switching circuit is not limited to the one using the -Funsfur gate as in the above-mentioned example, but various configuration examples can be considered.

[Field of Application] In the above explanation, the invention made by the present inventor will be mainly described in relation to State Inc.
Although the case where the application is applied to redundant circuit switching technology in M is described, the application is not limited thereto, and the application can also be applied to redundant circuits of semiconductor storage devices such as dynamic RAM and EPROM, and general semiconductor co-product circuits with fuses. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an example of applying the present invention to a redundant circuit of a memory. FIG. 3 is a circuit diagram showing a second embodiment in which the present invention is applied to a level setting circuit for redundant circuit switching. 1...Level setting circuit, 2...Y decoder, 3
... Passivation film, 4... Gate electrode,
5... Semiconductor substrate, 6... Gate insulating film, Q
p rQP'...Program element (MOSFET)
, R... High resistance element, Ql, Q2... Transfer/invasion N 1 Stomach 3 1

Claims (1)

[Claims] 1. An insulated gate field effect transistor formed on the main surface of a semiconductor substrate is used as a programming element,
A semiconductor device characterized in that programming is performed by short-circuiting between the gate electrode and the substrate by irradiating the gate electrode portion of the insulated gate field effect transistor with a laser beam. 2. The program element is a transistor formed at the same time as an insulated gate field effect transistor forming a circuit in a semiconductor integrated circuit having insulated gate field effect transistors as constituent elements. The semiconductor device according to item 1. 3. The semiconductor device according to claim 1 or 2, wherein the program element is a program element for switching a redundant circuit in a semiconductor memory device.