JPS609153A - Adjustment of resistance value of resistor inside semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To adjust the resistance value of a resistor to a resistance value, which is needed, by a method wherein a decrease or a increase of the resistance value is performed by that impurities of the same conductive type as that of impurities dopped the polycrystalline silicon resistor are further diffused in the resistor by performing a laser heating and the resistance value thereof is made to decrease, or, that impurities of the opposite conductive type are diffused in the resistor and the resistance value thereof is made to increase. CONSTITUTION:A polycrystalline silicon resistor 11, wherein impurities of an N type conductive type have been dopped, is formed on an Si substrate 1 through an SiO2 film 2 and both ends thereof are connected to other elements through Al wirings 12A and 12B. A polycrystalline silicon layer 14, wherein impurities of a P type conductive type have been dopped in a high concentration, is insularly formed on the polycrystalline silicon resistor 11 through an SiO2 film 13, and an SiO2 film 15, a phosphoric glass layer 16 and an SiO2 layer or an Si3N4 layer, or, a final passivation film 17 consisting of both of the SiO2 layer and the Si3N4 layer are formed thereon. Then, the phosphoric glass film 16 is irradiated with a laser beam through the SiO2 films 13 and 15, while the resistance value existing in a 10mum long part of the film 16 is being measured, and the irradiation is stopped at a point when a prescribed resistance value has been obtained, thereby enabling to adjust the resistance value to an arbitrary resistance value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for adjusting the resistance value of a resistor formed in a semiconductor integrated circuit using a radar.

[Background of the invention]

In recent years, there has been a demand for higher integration and higher performance for semiconductor integrated circuits. For this reason, a method has come to be used in which the resistance value of a resistor formed in a semiconductor integrated circuit is adjusted while measuring the overall characteristics after the semiconductor integrated circuit is completed. A laser is used to adjust this resistance value. This method is similar to methods commonly used to tune thick or thin film resistors formed on ceramic substrates. That is, as shown in FIG. 1, a part of a resistor 3 formed of nitride/tal, chromium silicon, polycrystalline silicon, etc. on a Si substrate 1 and insulated by a 5i02 film 2 is exposed to a laser beam 4. The resistance value between the electrodes 5A and 5B can be adjusted by removing it using As shown in FIG. 3, a method has been used in which the resistance value between the electrodes 5A and 5B is adjusted by cutting the ladder-like resistor 7.

However, all of these methods remove a part of the formed resistor and adjust by increasing the resistance value from the original value, so if the resistance value is higher than the required value, , was not adjustable. In addition, since the resistance value is adjusted after the semiconductor integrated circuit is completed, the entire circuit is coated with a matrix film, and the matrix removal film is also removed in the laser removal section, reducing reliability. From the point of view, it was necessary to coat the area again with a membrane.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art described above,
To provide a method for adjusting the resistance value of a resistor in a semiconductor integrated circuit, which is capable of not only increasing but also decreasing the resistance value created in advance, and which does not damage a passivation film.

[Summary of the invention]

In order to achieve the above object, the present invention provides a method for adjusting the resistance value of a resistor in a semiconductor integrated circuit, which is formed in a semiconductor integrated circuit, doped with a first conductivity type impurity to a concentration close to a predetermined value, and passivated. A film containing an impurity of a first conductivity type and a film containing an impurity of a second conductivity type opposite to the first conductivity type are provided near the polycrystalline silicon resistor covered with the film, and the passivation film is through,
When it is desired to lower the resistance value of the resistor, a predetermined region of the film containing the impurity of the first conductivity type is used, and when it is desired to increase the resistance value, a predetermined region of the film containing the impurity of the second conductivity type is The gist is to diffuse the impurity from the impurity-containing film toward the resistor by irradiating the region with a V-de beam and heating it, thereby lowering or increasing the resistance value. That is, the present invention uses polycrystalline silicon doped with impurities as a resistor, and further diffuses impurities of the same conductivity type as the impurities doped into the polycrystalline silicon resistor by Rade heating to reduce the resistance value. The resistance value is adjusted to a required value by reducing or increasing the resistance value by increasing the resistance value by increasing the resistance value or by diffusing impurities of the opposite conductivity type.

The resistance value of the resistor can be determined by irradiating a constant area on the resistor and changing the irradiation amount, or by keeping the irradiation amount per unit area constant and changing the irradiation area. To change the irradiation amount, it is convenient to change the irradiation time or the number of pulses.

Hereinafter, the present invention will be explained in more detail using examples with reference to the drawings, but these are merely illustrative and it is understood that various modifications and improvements may be made without going beyond the scope of the present invention. Of course.

[Embodiments of the invention]

FIG. 4 shows the steps for applying the resistance value adjustment method of the present invention.
A resistor formed on a semiconductor integrated circuit is shown. Figure 4 (
4(a) is a plan view, and FIG. 4(b) is a sectional view thereof. Si
A polycrystalline resistor 11 doped with an n-conductivity type impurity is formed on a substrate 1 via an Si02 film 2,
Both ends thereof are connected to other elements (for example, a diode f transistor) via At wirings 12A and 12B. A S'i02 film 13 is formed on the polycrystalline silicon resistor 11.
A polycrystalline silicon layer 14 heavily doped with p-conductivity type impurities is formed in the form of an island through the Si02
Layer 15. Phosphorous glass layer 16, Si02 layer or Si
A final/main ossification film 17 consisting of a 3'N4 layer or both is formed.

Generally, the polycrystalline silicon resistor 11 has a thickness of 50 to 500 nm and is doped with phosphorus as an n-conductivity type impurity.
The sheet resistance value is set to several tens of Ω/hole to several hundreds of Ω/hole. The 5i02 layers 13 and 15 each have a thickness of 50 to 300 nm, and the polycrystalline silicon layer 14 doped with p-conductivity type impurities has a thickness of 50 to 500 nm and has an impurity concentration similar to that of the resistor 11. The phosphorus glass film 16 has a phosphorus concentration of 1 to 10% and a thickness of 10 to 11%.
000n, the final passivation film 17 is 100~4
The thickness is 000 nm.

Here, as a sample, the polycrystalline silicon resistor 11 is made of polycrystalline silicon doped with phosphorus, and is formed to have a film thickness of 300 nm, a sheet resistance value of 10 Ω/hole, a width of 511 m, and a length of I μm. 15 has a film thickness of 7
゜nm, the phosphor glass film 16 has a thickness of 4 mm and a film thickness of 40 mm.
0 nm, and the passivation film 17 is 5t3N.
.

A single layer film with a thickness of 1000 nm was used.

A predetermined region of the polycrystalline silicon resistor shown in FIG.
Irradiate with a laser beam using the optical system shown in the figure. That is, the optical system shown in FIG. 5 uses a variable slit 22 that can shape the Raded light 21 oscillated by a laser oscillator (not shown) into a rectangular shape that matches the shape of the irradiation onto the resistor 11. (The objective lens is adjustable)
The object lens n is transmitted through the insulating films 17, 16, 15°13 to the resistor 11 placed at a position where it forms the real image of 22.
It is configured to collect and project light at a magnitude that is the reciprocal of the magnification. Note that in FIG. 5, the layer formed on the resistor 11 is omitted. The laser oscillator is an N2 Rade pumped Gui laser, and the wavelength of the Rade light is 51
0 nm, and the pulse width is 6 ns at half width.

Here, with respect to the polycrystalline silicon resistor 11 shown in FIG. A radar was projected onto a portion having a length of 10 μm through which the phosphor glass film 16 was present. The relationship between the number of irradiation radar pulses and the resistance value at this time is shown in FIG. The resistance value, which was approximately 60 Ω before the radar irradiation, decreased with the number of irradiation pulses, showing a relatively rapid change at 1 O-(9) arm pulse, and after the I pulse, it reached a constant value of 41 Ω. There was almost no change. From this, by irradiating with the Rade beam without measuring the resistance value and stopping the irradiation when the predetermined resistance value is obtained, it is possible to
It is possible to adjust the resistance value to any value between (although it changes stepwise rather than continuously because it is based on pulse irradiation).

Next, a 5i02 film 15, a phosphorus glass film 16, and a phosphorus glass film 16 are formed on the polycrystalline silicon resistor 11 shown in FIG. A length of 5μ is passed through the passivation film 17.
irradiated with a laser beam within an area of m. The relationship between the irradiation radar number and the resistance value at this time is shown in FIG. The resistance value, which was about 60Ω before radar irradiation, decreased to 30-60Ω.
It showed a relatively rapid change at 4' rus, and after 70 rus, it had a constant value of Ω of 84, with almost no change.

From this, by stopping radar irradiation when a predetermined resistance value is obtained, any resistance value between 60Ω and 84Ω can be achieved (Due to Cruz irradiation, it is not continuous but gradual. ) can be adjusted. That is, by selecting the radar irradiation position for the polycrystalline silicon resistor shown in FIG.
The resistance value can be adjusted to any value between .about.84.OMEGA. At this time, the irradiation laser power density was set to 1 to 2 nm, so that it would be possible to remove the polycrystalline silicon resistor 11 with a laser beam of 1 to 2 nm. No damage or traces of passivation film 17K were found.

In the embodiment described above, the adjustment range of the resistance value is approximately ±30% with respect to the initial value, but this adjustment range is variable depending on the configuration of the polycrystalline silicon/resistor 11 and its surroundings. That is clear. That is, the direction connecting the long electrodes 5A and 5B covering the polycrystalline silicon/resistor 11 of the island-shaped polycrystalline silicon layer 14 doped with p-conductivity type impurities formed on the polycrystalline silicon resistor 11 ) and increase the length of Karede irradiation, or by increasing the impurity concentration of the island-shaped polycrystalline silicon/layer 14 doped with p-conductivity type impurities, the resistance value can be adjusted to a higher value. In addition, by increasing the portion (length) that is not covered by the island-shaped polycrystalline silicon layer 14 doped with p-conductivity type impurities and increasing the length over which the radar is projected, the resistance value can be reduced. can be adjusted to a lower value.

Furthermore, in this embodiment, polycrystalline silicon doped with n-conductivity type impurities was used as the polycrystalline silicon resistor 11, but polycrystalline silicon doped with p-conductivity type impurities was used as the resistor. By using an island-shaped polycrystalline silicon layer doped with an n-conductivity type impurity and forming boron glass instead of phosphorous glass, the resistance value can be increased or decreased in the same way. It is clear that this can be done.

In the above embodiment, a film containing an impurity of the same conductivity type as the polycrystalline silicon resistor 14 (the phosphor glass layer 16 in FIG. 4(b)) is also a film containing an impurity of the opposite conductivity type (FIG. 4(b)).
), the polycrystalline silicon film 14) is also provided on the polycrystalline silicon resistor 14, but these films do not necessarily have to be on the resistor 14, and when heated by the Rade beam, The impurities contained in the insulating film surrounding the resistor 14 (in FIG. 4(b), 5i02
If it is close enough that it can diffuse through the film 13 or 5i02 films 13 and 15) to the polycrystalline silicon resistor,
Of course, it may be placed on the side or below.

Further, in this embodiment, N2 Rade excitation die Rade is used as the Rade light 21, but the invention is not limited to this.
It is clear that any device that can heat polycrystalline silicon with a wavelength that passes through the 6, 5i02 films 15, 13 can be applied regardless of continuous oscillation or Noculus oscillation. When the passivation film 17 is SiO□, the film 1
5, 16, 17 are all 5i02, 300n
It is transparent to wavelengths of m to 2 μm. When the passivation film 17 is Si3N4, the films 15, 16, 1
7 is transparent to wavelengths of 400 nm-2 μm.

If the laser light is not transparent to the films 15, 16, and 17, the Rede light will be absorbed by those films.
Not only will the temperature of these films increase and damage occur, but the polycrystalline silicon layer will not be able to provide the energy necessary to heat it. When the wavelength is 1.1 μm or more, the Rede light passes through the SS and does not heat the polycrystalline silicon layer, so the wavelength of the Rede light used is 400 nm, which is 1.1 μm.
Must be between μm.

The 5i02 films 13 and 15, which are the intermediate permeable layers, are made of phosphorus silicade or? However, as long as no pinholes are formed in the final passivation film 17 or removed, this does not pose a problem for the integrated circuit as a whole.

FIG. 8 is a plan view for explaining a method for adjusting the resistance value of a resistor in a semiconductor integrated circuit according to a second embodiment of the present invention. As shown in FIG. 8, the length of the laser irradiation area 24A on the polycrystalline silicon resistor 11 shown in FIG. 4 is set to 2 μm.
Then, the concave surface was irradiated with nine lass under the radar irradiation conditions described earlier,
Next, the laser irradiation area is moved by 2 μm, and the laser irradiation area 24B is irradiated with Kasosolus. By repeating this step by step, the resistance value decreased step by step. In other words, as shown in Figure 9, the number of irradiations (in each radar irradiation area)
The initial value of 60 Ω decreased by Ω to about 3.8, and decreased to 33 kΩ after 7 irradiations. The length of the irradiation area at this time was 14 μm.

Moreover, on the island-shaped polycrystalline silicon layer 14 provided on the polycrystalline silicon resistor 11 and doped with an impurity different from the impurity doped into the polycrystalline silicon resistor, the 7Q z of each radar irradiation area according to the procedure
The resistance value increased stepwise by irradiating each f las. That is, by selecting the irradiation position for the polycrystalline silicon resistor shown in FIG. 4 (or FIG. 8), the initial resistance value can be increased or decreased as desired.

Furthermore, in this embodiment, the case where laser irradiation is performed using the optical system shown in FIG.
It is clear that exactly the same effect can be obtained by repeating the procedure of 50/4 or 70 Hals irradiation, moving the irradiation position, and further performing radar irradiation.

〔Effect of the invention〕

As explained above, according to the present invention, the resistance value of a resistor in a semiconductor integrated circuit can be increased or decreased arbitrarily without damaging the d' tsivation film, resulting in high performance and high reliability. It is possible to produce semiconductor integrated circuits with high yield.

[Brief explanation of the drawing]

1 to 3 are perspective views for explaining three different conventional methods for adjusting the resistance value of a resistor in a semiconductor integrated circuit, and FIG. 4(a) and fbJ are perspective views for explaining the resistance value adjustment method of the present invention. FIG. 5 is a plan view and a cross-sectional view of a resistor formed on a semiconductor integrated circuit for applying the method, FIG. 5 is a perspective view of a laser optical system for implementing the resistance value adjustment method according to the present invention, and FIG. Figure 7 and Figure 7 are diagrams showing the relationship between the number of irradiation pulses and the resistance value of the resistor when a region of the opposite conductivity type and a region of the same conductivity type as the resistor are irradiated with a Rade beam, respectively. Plan view for explaining the resistance value adjustment method according to another embodiment of the present invention, No. 9
The figure is a diagram showing the relationship between the number of irradiations and the resistance value of the resistor in the embodiment shown in FIG. l...si substrate, 2...5i02 film, 11...n
Type polycrystalline silicon resistor, 1.2A, 12B,...
Electrode, 13, 15-5i02 film, 14... p-type polycrystalline silicon layer, 16... phosphorus lath film, 17... final hassipation II! , 21... Ray f' light, 22
...Variable slit, n...Objective lens, 24A, 2
4B...Laser irradiation area. Agent Patent Attorney Tadashi Akimoto Actual 1st, 2nd, 3rd, 4th (a) (b) 5th, 6th, ρC, Ha, Rusu, Φki, 70th, 1st, 2nd, 3rd, 4th (a) (b)

Claims (1)

[Claims] 1. A polycrystalline silicon/resistor formed in a semiconductor integrated circuit, doped with a first conductivity type impurity to a concentration close to a predetermined value, and covered with an IP coating/film. A film containing an impurity of a first conductivity type and a film containing an impurity of a second conductivity type opposite to the first conductivity type are provided nearby, and it is desired to lower the resistance value of the resistor through the passivation film. When it is desired to increase the resistance value, the predetermined region of the film containing impurities of the first conductivity type is
By irradiating a predetermined region of a film containing conductivity type impurities with a Rade beam and heating, the impurities are diffused from the film containing the impurities toward the resistor, thereby reducing or increasing the resistance value. A method for adjusting the resistance value of a resistor in a semiconductor integrated circuit, characterized in that: 2. The semiconductor according to claim 1, wherein the irradiation is performed over a constant area of the resistor, and the resistance value of the resistor is controlled by controlling the degree of diffusion. A method for adjusting the resistance value of a resistor in an integrated circuit. 3. The resistance value of the resistor in the semiconductor integrated circuit according to claim 2, wherein the degree of diffusion of the impurity is controlled by controlling the irradiation time or the number of pulses of the V-de. Adjustment method. 4. The method of adjusting the resistance value of a resistor in a semiconductor integrated circuit according to claim 1, wherein the resistance value of the resistor is controlled by controlling the area irradiated with a Rade beam.