JP3089644B2 - Semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a technology effective when applied to a nonvolatile memory using a Schottky barrier diode.

[Conventional technology]

One of the nonvolatile memory structures using a Schottky barrier diode is to form an intrinsic silicon film on the Schottky barrier diode as shown in FIG.
As shown in the figure, there is a structure arranged in a lattice. One cell is formed of a switch and a diode, and discriminates information based on ON / OFF of the switch. This structure is 1TIMEPR
OM (Electrically writable nonvolatile memory only once)
It is said that. In FIG. 4, the diode is a Schottky barrier diode. The diodes, when arranged in a grid, serve to block current from other cells. In addition, the intrinsic silicon film plays a role in the switch. That is, before electrical writing, the intrinsic silicon film has a high resistance, so that a small amount of current flows when a voltage of about 5 V is applied, so that the switch is turned off. When writing is performed electrically, that is, when a voltage of about 20 V is applied to the intrinsic silicon film, the intrinsic silicon film is broken and a current easily flows, so that the intrinsic silicon film is turned on.

1 TIMEPROM before the destruction of the intrinsic silicon film
Information is extracted based on the magnitude of the later current value.

[Problems to be solved by the invention]

However, the conventional technique has a problem that it cannot be miniaturized. In addition, there is a problem that the information extraction current value greatly differs depending on the cell arrangement position and the same switch is turned on.

As described above, 1TIMEPROM determines information based on the magnitude of current. That is, the greater the difference in the current, the more the sensing capability of the current sensing circuit connected to the cell is allowed, and the more accurate the operation can be made. Also, circuit design becomes easy. Also, it can cope with product variations of mass-produced products.

In the prior art, the silicon film into which the impurity of the Schottky barrier diode is implanted also serves as the wiring in one side of the lattice. The wiring in the other direction of the lattice was formed of an aluminum film on the intrinsic silicon film. For miniaturization, both wirings are formed as thin as possible. Although the sheet resistance of aluminum is as small as 30 mΩ / □ or less, the sheet resistance of the silicon film implanted with the impurity forming the Schottky barrier diode is 1000Ω / □.
□ Very high. To reduce the resistance, a large amount (1
× 10 ²² cm ^-3 or more), 100 Ω /
□ It is possible to make it as low as possible. However, if the amount of impurities is increased, the diffusion current, which is the reverse current of the Schottky barrier diode, increases, and it becomes impossible to block the current from other cells.

Therefore, since the resistance value of the silicon film into which the impurity is implanted is high, when the cells are arranged in a lattice, the parasitic resistance value greatly differs depending on the position of the cell from the current sensing circuit. Even in the same state, there is a problem that the value of the information extraction current value is greatly different between the cell near the current sensing circuit and the cell far from the current sensing circuit, and it is difficult to sense.
In order to lower the resistance value of the silicon film into which the impurity has been implanted, the line width must be increased, so that miniaturization is difficult. Further, it has been confirmed by the present inventor that when information is written, that is, when the intrinsic silicon film is destroyed, there is a difference in the current after the breakdown due to the current at the time of the breakdown. The larger the current flowing through the intrinsic silicon film at the time of breakdown, the greater the current after breakdown. Therefore, a cell having a high parasitic resistance value has a problem that since the current at the time of destruction is small, the current difference between the information extracting current before and after the writing becomes smaller, and it is difficult to detect the current.

Therefore, the present invention solves such a problem.
It is an object of the present invention to provide a Schottky barrier diode that can be miniaturized, can operate stably, and can cope with product variations of mass-produced products, and a memory using the same.

[Means for solving the problem]

The semiconductor device according to the present invention includes a first insulating film provided on a semiconductor substrate, a first silicon film implanted with a group III or V impurity, and provided on the first insulating film; A second insulating film provided on the film and having a contact hole; a metal film provided on the first silicon film exposed by the contact hole and forming a Schottky barrier diode together with the first silicon film; The second so that it passes over the contact hole
A wiring layer provided on an insulating film, wherein an impurity element having a concentration higher than that of the impurity element implanted in the first silicon film is implanted under the first silicon film. A second silicon film is formed.

The semiconductor device of the present invention may further include a second silicon film formed in the semiconductor substrate, a first silicon film implanted with a group III or V impurity, and disposed on the second silicon film. A second insulating film provided on the first silicon film and having a contact hole; and a metal film provided on the first silicon film exposed by the contact hole and forming a Schottky barrier diode together with the first silicon film. And a wiring layer provided on the second insulating film so as to pass over the contact hole, wherein the second silicon film is formed by being injected into the first silicon film. The impurity element is implanted at a higher concentration than the impurity element concentration.

〔Example〕

FIG. 1 is a sectional view of a semiconductor device according to one embodiment of the present invention. 2 (a) to 2 (d) are main cross-sectional views for each manufacturing process.

In all the drawings of the embodiments, those having the same functions are denoted by the same reference numerals, and the repeated description thereof will be omitted.

Hereinafter, description will be given with reference to FIGS. 2 (a) to 2 (d). Here, for convenience of explanation, an example using an N-type Schottky barrier barrier diode will be described.

First, as shown in FIG. 2 (a), a CVD
The first insulating film 2 is formed by a method (chemical vapor deposition).
About 2000 Å of SiO ₂ film would be appropriate. And the first
A polycrystalline silicon film 3 (second silicon film) is formed on the insulating film 2 by a CVD method at a thickness of about 3000 °. Usually, polycrystalline silicon is deposited by thermal decomposition of monosilane gas. Then, in order to reduce the resistance of the polycrystalline silicon film 3, for example, a phosphorus element is ion-implanted into 6 × 10 ¹⁵ atoms · cm.
Inject ^-2 or more. Arsenic may be used instead of phosphorus.

Next, as shown in FIG. 2B, a second polysilicon film 5 (first silicon film) is formed in the same manner as the first polysilicon film 3 for the N-type silicon film of the Schottky barrier diode. Deposit 3000 mm. And to make it N-type,
For example, phosphorus element is implanted using an ion implantation method.
The amount of DOSE for this ion implantation affects the characteristics of the Schottky barrier diode and must be carefully determined. In the reverse direction, the current needs to be small and the sheet resistance value needs to be small, so that 1 × 10 ¹³ to 1 × 10 ¹⁴ atoms · cm ⁻² is appropriate. Then, in order to activate the impurities of the first polycrystalline silicon film 3 and the second polycrystalline film 5, it is heated in an N ₂ atmosphere. 1000 ° C 60 using a halogen lamp
Heat for about a second.

Next, as shown in FIG. 2 (c), a second insulating film is formed as an interlayer insulating film.
An insulating film 7 is formed. For example, CVD, an SiO ₂ film 300
It is appropriate to form about 0 °. Then, the second insulating film 7 where the Schottky barrier diode is to be formed is removed by a photo and etching method. Etching is performed with a hydrofluoric acid solution or the like using an organic resist that is usually used when manufacturing a semiconductor device.

Then, for example, titanium 8 is formed on the entire surface by a sputtering method, and heated at 700 ° C. for about 60 seconds using a halogen lamp. As a result, the titanium at the portion where the second insulating film 7 has been removed reacts with the second polycrystalline silicon film 5 therebelow to become titanium silicide. Thereafter, the titanium other than the titanium silicidized portion is etched by a mixed solution of ammonia, water, and hydrogen peroxide solution.

Next, as shown in FIG. 2D, an intrinsic silicon film 9 serving as a switch is formed. Similarly, the first polycrystalline silicon film 3 and the second polycrystalline silicon film 5 are formed to have a thickness of 2000 ° by the CVD method. Then, unnecessary portions are removed by a photo and etching method.

Finally, as shown in FIG. 1, a lead wiring 10 is formed on the second insulating film 7 and the intrinsic silicon film 9. It would be common to form aluminum by sputtering and remove unwanted portions by photo and etching.

 Through the above steps, an embodiment of the present invention is obtained.

As described above, by forming a silicon film having a small resistance under the silicon film of the Schottky barrier diode, the parasitic resistance is drastically reduced. Therefore, regardless of the placement location, the parasitic resistance is small and the difference between the drawn current values before and after writing becomes large,
It is possible for the current sensing circuit to accurately determine the information. Also, when writing information, that is, when destroying the intrinsic silicon film, a large current can flow,
It is possible to reduce the resistance value after destruction. Further, since the impurity amount of the silicon film of the Schottky barrier diode can be arbitrarily determined, the impurity amount can be determined so as to have the best relationship between the applied voltage and the output current value. In the present embodiment, titanium is used as the metal film of the Schottky barrier diode. However, platinum, tungsten, or the like may be selectively formed on the second silicon film.

Further, the silicon film having a small resistance value can also serve as a gate electrode of an element already formed in a lower layer, for example, a transistor or the like.

As another embodiment, the same effect can be obtained by implanting a high concentration impurity into a semiconductor substrate instead of the polycrystalline silicon film 3 and forming the second polycrystalline silicon film 5 thereon. It is possible to get.

〔The invention's effect〕

As described above, according to the semiconductor device of the present invention,
By forming the impurity-containing silicon film at a higher concentration under the impurity-containing silicon film of the Schottky barrier diode, the wiring parasitic resistance is reduced. Therefore, miniaturization and stable operation can be performed, so that the present invention can be applied to a memory, and the reliability of the memory is improved.

[Brief description of the drawings]

FIG. 1 is a main sectional view showing one embodiment of a semiconductor device of the present invention. 2A to 2D are main cross-sectional views for explaining an example of a method for manufacturing a semiconductor device of the present invention in the order of steps. FIG. 3 is a main sectional view showing a conventional semiconductor device. FIG. 4 is a circuit diagram of a one-time electrically writable nonvolatile memory using a Schottky barrier diode. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2 ... 1st insulating film 3 ... 1st polycrystalline silicon film 4 ... 1st impurity ion beam 5 ... 2nd polycrystalline silicon film 6 ... 2nd impurity ion beam 7 ... 2 Insulating film 8 Titanium 9 Intrinsic silicon film 10 Aluminum wiring

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 27/10 431 H01L 29/872

Claims (5)

(57) [Claims] A first insulating film provided on a semiconductor substrate; a first silicon film implanted with a group III or group V impurity and provided on the first insulating film; A second insulating film having a contact hole, a metal film being provided on the first silicon film exposed by the contact hole and forming a Schottky barrier diode together with the first silicon film; A wiring layer provided on the second insulating film so as to pass therethrough, wherein a concentration of the impurity element implanted in the first silicon film under the first silicon film is lower than that of the impurity element implanted in the first silicon film. A second silicon film into which a high concentration impurity element is implanted. 2. The semiconductor device according to claim 1, wherein said metal film contains a high melting point metal. 3. The semiconductor device according to claim 1, wherein a third silicon film is provided between said metal film and said wiring layer. 4. The semiconductor device according to claim 3, wherein said Schottky barrier diode is formed at an intersection of said second silicon film formed in a lattice and said wiring layer. . 5. A second silicon film formed in a semiconductor substrate; a first silicon film implanted with a group III or V impurity and disposed on the second silicon film; A second insulating film provided on the first silicon film and having a contact hole, a metal film provided on the first silicon film exposed by the contact hole and forming a Schottky barrier diode together with the first silicon film; A wiring layer disposed on the second insulating film so as to pass over the hole, wherein the second silicon film has a concentration of an impurity element implanted into the first silicon film. A semiconductor device in which an impurity element having a higher concentration is implanted.