JPS58171833A - Wiring connection by laser beam - Google Patents

Abstract

PURPOSE:To realize wiring connection with high quality and high yield without damage on the wirings by changing the wiring portion to the conductive condition from non-conductive condition through irradiations of laser beam in plural times at a low power intensity. CONSTITUTION:The wiring portion insulated from a substrate 1 by a SiO2 film deposited on the substrate 1 is composed of low resistance layers 3, 4 and a high resistance layer 5 and moreover it is configurated with formation of insulating films 8, 9, 10 in addition to them. In case of connecting this connecting portion, the laser beam is condensed and irradiated to the high resistance layer 5 and the low resistance layers 3, 4 in both side thereof with the not indicated optical system, in view of changing the high resistance layer 5 into the low resistance layer. The laser beam is irradiated pulsively for several times in such a density as 3/4 or less of the minimum value of the power density which is enough for cutting the Si wiring with one pulse. Thereby, wiring connection can be realized with high quality and yield without generating any damage on the wiring portion even if the laser oscillator output is fluctuated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting wiring within a semiconductor integrated circuit.

By cutting or connecting (short-circuiting) a portion of the wiring of the integrated circuit, it is possible to program (circuit change)' on a manufactured integrated circuit chip.

Traditionally, this program was run in read-only memory (
Programming of ROM (ROM), or recently, ROM is used to repair defective cells in memory devices.

The following methods are known as these conventional methods: (1) Cutting specific portions (fuses) of wiring made of PoIy-8i, AI, nichrome, etc. using electric current.

(1) A specific portion of the wiring of PoIy-8t, AI, nichrome, etc. is cut by applying energy to a laser or optically from the outside.

These both cut a part of the wiring and require a large amount of energy, and the PoIy-81 and wiring metal can easily damage nearby SiO and films, and the laser beam can easily damage the substrate. . Also, if the EJIin is covered with a passivation film (81(h, 81N)), part of the passivation film on it will be removed when cutting the wiring, so it is necessary to re-coat the passivation film. There were some drawbacks such as not being able to do so.

On the other hand, as a method for eliminating these drawbacks, a method has been proposed in which specific portions of the wiring are connected (short-circuited), as shown in FIG. That is, the cap in Figure 1 is adhered to the &substrate 1 and 9010
2 ON 10-shaped PoI isolated from substrate 1 by layer 2
The y-8l (polycrystalline 81) layers 3 and 4 are opposed to each other with an intervening layer consisting of an extremely high resistance (e.g., 5ooKQ or higher) PoIy-81 layer (strong even if not doped with impurities). The wiring structure is By irradiating this with a laser spot such as 6 and giving sufficient energy, diffusion is caused from the n-domain layer S, 4, and the first
wA<8), high-resistance eyebrow ink is converted into a low-resistance layer 1. According to the above, before laser irradiation, the n-domain layers 3 and 4 are
were in a non-conductive state, but after irradiation, the +-type layers 3 and 4 changed to a conductive state, completing the wiring connection (short circuit).

However, in this method, although the laser irradiation power density is lower than in the cutting method, it is necessary to cause impurity diffusion in a short time. Layer 3.4 must be heated to a very high temperature. On the other hand, if the Atb temperature is too high, it will damage the PoIy-Si layer, and in extreme cases it will break.◇For this reason, the connection (short circuit)
The range of laser conditions (irradiation power density) for performing this is extremely narrow. i.e. due to variations in laser power, connections (short circuits)
The disadvantage is that the yield is low.

The object of the present invention is to eliminate the above-mentioned nine drawbacks of the prior art, and to
OM (Bead O!IIF M@rmory)
, PLM (ProgramabI* Logi
It is an object of the present invention to provide a method that can perform wiring connections (short circuits) with high yield, which can be applied to programming a memory device or relieving defects in semiconductor devices including memory elements.

That is, the present invention provides irradiation multiple times (preferably 01 times or more) at a low power density that does not cause damage to the wiring part (PoIy-81 layer) even if there is some variation in laser output. Additionally, high-quality connections can be made at a high yield without causing any damage to the wiring section.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 3 shows 8102 layers coated on the mother substrate iris and 91 n-type PoIy-1!11 insulated from the substrate 1.
The (polycrystalline silicon) layer 3.4 has an extremely high resistance (for example, 1."Q/gate or higher) and faces each other with a P@Iy-111 layer 11 (not doped with impurities and very thick) interposed therebetween. The N+ type layer 3.4 and the 1st layer are connected to the C! The thickness of the 16?-11 layer is 11 m, and the n-type layer 1.4 is doped with phosphorus or arsenic to an impurity of 1 degree 1 (1"/cj or more. Also, the insulating layer is 11 m thick. The thickness is ■～...1
Peng0IilO* film, insulation-.

contains 1 to 10we IX of phosphorus, 10111-,
=1 @...Kamewa (01~1-) phosphorus glass film (
P 11 G film), the thickness of the insulating layer is 1%-
4＠＠omm (os-4μm) of 81 (ht or 81N or one layer thereof; b final insulating material (FlnaI Passivalom l [
).

A laser beam is irradiated onto the beam distribution section shown in Fig. 3 using the optical system shown in Fig. 3. That is, the optical system shown in FIG. 3 emits laser oscillation l! (not shown) A variable slit (not shown) that can change the oscillated water laser beam 11 to any size is arranged in a rectangular shape, and the variable slit (11) is formed into a rectangular shape by the objective lens (not shown). Wiring connection part placed at the position where the actual wiring is connected (as shown in Figure 3, the board' * 5i02
Sandwiched between the n-type P/IF-81 layer 3.4 formed on layer 8 and 9! Insulating film 1. The structure is such that the light passes through the light beams # and 1, and is focused and irradiated by the reciprocal of the objective lens tSO magnification. Insulating film l.

9, total thickness of violet 14 (1,1-@fi111
It is transparent to wavelengths in the visible range, and absorption loss can be almost ignored.

With the optical system shown in the jls diagram, PoIy-81 wiring a
, a, s (wiring width!71111.i layer S length 4μ
For ma), the laser was irradiated to the area of 3 voices mX1@J1m. In this case, the length of the i-layer layer is 4 μmM, so the n-domain PoIy-8 layer (low resistance layer) on both sides
The laser beam is irradiated to each ladle.

Figure 4 shows the irradiation results using a laser with a pulse width of fnms and a wavelength of 1. The vertical axis shows the relative power density, and the horizontal axis shows the irradiation power density. In the case of conditions above 0, that is, curve 1, which indicates the state of the wiring III connection, the energy of the irradiated laser causes excessive rounding, and the wiring is severely damaged, resulting in a disconnection or near disconnection. In addition, under the conditions below in Song III! (The shaded area) indicates that the connection can be made.Here, the connected state means a high resistance PoI
The resistance value of y-81 layer m (1 layer) decreased to 101Ω or less, indicating a good condition. This is due to the high resistance Po before laser irradiation.
1y-81 layer l0 resistance value 10-Ω or more compared to
If the change is 4 or more, it can be considered as a complete short-circuit condition. It is easy for the high resistance PoIy-81 layer (5 layers) 5 to lower its resistance by laser irradiation because the 01 layer and the n”ffi PoIy-8 layer 1゜4 on both sides of it are high temperature when exposed to laser light. ri, n'jlPoI
The impurity (phosphorus) in the y-81 layer 14 easily diffuses into the 1 layer.
Eyebrow ink changes to n layer.

fwa 1 layer and 1 type PoIy-81 layer 3 on both sides
゜4 becomes high temperature due to the laser beam, and the insulating film -9 that is in contact with them also becomes high temperature, and the phosphorus in the insulating film easily diffuses into the layer below it, causing the layer 1 to become the n layer. Change.

This is thought to be due to one or both of the following.

As is clear from FIG. 4, connection could not be established with one pulse irradiation. That is, when the relative density is higher than Po1
This is because the Y-81 layer is cut and phosphorus does not diffuse sufficiently when the relative power density is less than 1. With 2-pulse irradiation, connection could be made with a relative power density of Q, 9, but in general, depending on the laser preference (the pulse output is ±s even if it is stable)
Because of the variation of about X, the PoIy-8 layer may be cut or not connected, resulting in a low connection yield. For S pulse irradiation, the relative power density is Q, ? By setting it as desired, we were able to connect with a high yield rate.

Furthermore, if the number of irradiation pulses is increased, connections can be made with lower relative power densities while still allowing acceptable laser
The width of pulse variation is large. In general, in a pulsed laser, the variation between pulses is more than ±l·, and temporal variations are also added to this. Additionally, process variations, ie, variations in film thickness and impurity concentrations from wafer to wafer or from lot to lot, have the same effect as relative variations in laser pulse output. Therefore, a more stable connection can be achieved by setting the relative power density low and irradiating a large number of pulses. for example,! 1/ of the lowest power density that can cut the PoIy-8 layer with a pulse! , that is, the relative power density (1,1, 2
When irradiating 0 pulses, the laser pulse is ±30%
It is possible to reliably connect even if there are variations above. Furthermore, in the case of irradiation with a relative power density of 0 and 4.10g one pulse, a variation of 10X or more is allowed.

As mentioned above, the results shown in Figure 4 are for the case where the width of one layer 6 is 0 μm and the length is 4 μm. The density or number of pulses is required, and the curve 1 in FIG. 4 shifts to the upper right. On the other hand, if the thickness and width of one layer do not change, the curve m1
If llB is left as is, the range of conditions under which it can be connected becomes narrower. However, even if the length of one eyebrow ink is to pH, the relative power density is 04.1 @ pulse irradiation! D.
Adequate connections and laser pulse variation of ±1
9 allowed with 0XMj. When the thickness of the first layer S changes, the curve 1s shifts. That is, if the thickness increases, the curve II shifts to the upper right, and if the thickness increases, the curve II shifts to the lower left. However, if the thickness of one layer 6 is ■・nm4 degrees or more,
Enough connections can be made.

The embodiments described above are based on the case in which the nine optical systems shown in FIG. It is possible to prevent the laser from being irradiated on the
The present invention is not limited to this optical system.

A third example will be shown below. Figure S is n-decade PoIy-
A plan view of the wiring connection section consisting of the 81st layer 8.4 and the 95th layer sandwiched between them (for simplicity, insulation l11g,
., 1G are omitted), but a method is usually used in which a laser beam is focused on a fine spot 1yK by an objective lens and irradiated. Even in this sophisticated method, the center of the condensing spora )ll and the center of the 1st eyebrow ink are made to almost match, and each condensing spot is at least n-shaped PoIy-8t jll
Connection can be made by irradiating s and a in a double-null-like manner.

In this case, the range in which a good connection can be made is narrower than the condition range shown in FIG. In other words, the power density distribution at one focused spot is a Gaussian distribution,
The average power density is higher in the center and lower in the periphery, so song 1! II to the lower left, curve l
・Shifts to the upper right. However, when a laser beam focused to a spot diameter of approximately .mu.m is used as a go pulse with an average power density (relative value) of 0.4, the average power density (relative value) is 0.4.
Is there enough connection by irradiating 100 pulses at 3? I was able to do that.

Next, Figure 6 showing another example is similar to Figure 1lls,
. Hand-carved PoIy-8i layer 1.4 and their 91
This is a plan view of a wiring connection section made of a layer S. A laser beam is focused on a fine spot 1 by an objective lens and irradiated thereon. In this case, the focused spot weight is about the same as the width of the wiring section,
In other words, the width of the wiring portion and the positioning accuracy are taken into consideration.

In this example, the wiring width is 0 μm and the positioning accuracy can be ±1 μm, so the spot diameter is 1 μm.
~4 μmφ is optimal. This light condensing spora) (1) is scanned relatively to the nx type PeIy-81 layer 4 through the nx type PoIy-81 layer 1 or 11, for example, in the area shown in the figure. As a scanning means, it is also possible to move a 9X-Yx stage on which a wafer (in the form of a chip) is placed, or to scan with a laser beam using a means such as a galvanometer mirror or a rotating polygon mirror. A Q-switched YAG laser with 8th harmonic (wavelength: 182 nnl, pulse width: 3 axes) is used as a laser, and the average power density (relative value) is approximately 4 μmφ with an average power density (relative value) of 0.4.
The light was focused on a spot and scanned over a square with a spot pitch of 1 μm at a repetition rate of IKH. When the scanning distance was 6 .mu.m (-scan T pulse), good connection was obtained by scanning three or more times in the case of a long I-layer.

Similar results were obtained not only by scanning in a fixed direction but also by reciprocating irradiation (-reciprocating is considered as two scans). If the length of the first layer S is long, the power density will be increased, but it is possible to connect by increasing the number of scans. Density (relative value) o, s, @sufficient connections can be made with ＠times of scanning.

In this embodiment, as in the 10th embodiment, the connection part of wiring line II is irradiated with almost uniform laser power, and
This also has the effect of preventing laser irradiation to parts other than the I-connection part.

In the embodiments described above, n-type Po1y-8
i -1NFn decagonal PoIy-81 layer (n+-5-n+
), but we have only explained the structure of
y-81 layer-1 layer-P decaoid-PoIy-8l layer (p+-
Exactly the same effect can be obtained with the configuration t-p+). In this case, Bone glass I is used as the insulating film.
I (BSGj [) is] 1itL. 9P 10P
oIy-81 layer-1 layer-n decadal PoIy-81 layer (p+
The purpose can also be achieved by forming a Pn diode according to the configuration of J). in this case,
The insulating film may be either phosphor glass or boron glass.

Furthermore, as a laser, n2 laser excitation D7・ray fTo
First, we will explain the case of using the third harmonic of a Q-switched YAG laser. Zuno fundamental wave @xe
laser, metal vapor radar, excimer laser, ruby laser, cavity damping pulsed Ar or Kr laser.

It is clear that similar advantages can be obtained by using a transparent laser for the insulating film 1, 1, 1, etc. using various types of pulsed laser excitation or flash lamp excitation. As described above, according to the present invention, even if the output Std of the laser oscillator fluctuates, the connection can be performed with high quality and high yield without causing damage to the wiring portion.

[Brief explanation of drawings]

FIG. 1 is an explanation F of a conventional technique for connecting specific parts of wiring, FIG. 8 is a diagram showing a general configuration of a wiring connection part in which the present invention is implemented, and FIG. FIG. 4 is a diagram showing the optical system, FIG. 4 is a diagram showing an appropriate condition range, and FIG. 6 is an explanatory diagram showing another embodiment of the present invention. 1...81 substrate 2...8102 layers 3.4...
Ten-shaped PoIy-St layer S...High resistance layer (1 layer)
6... Laser beam 8... 5to2 film 9...
・PIG film 10... Final insulating film (FlnaI
Passivation film) 1. Variable rectangular slit 13. Objective lens Figure 1 (A) (B) Singing 2. (U car 4 figure!!

Claims (1)

[Scope of Claims] 1. Laser light is applied to the wiring part doped with a hydrogen impurity and which is in a non-conducting state due to the high resistance part formed in a part of the multi-connection set of wiring in the low resistance part. Apply a power of 11J1, which is less than the minimum value of μ at a time, to the same part of the high-resistance part and at least a part of the low-resistance part on both sides of the same part. A wire connection method using a laser, characterized in that the wire connection within a semiconductor device is performed by concentrating and irradiating stroke pulses to change the wiring portion from a non-conducting state to a conductive state. A shaped slit is formed into a rectangular shape of arbitrary size, and an objective lens is used to collect and irradiate light as a reduced image of the rectangular slit.Arrangement 1! 4 II to carry out a continuation
Wiring connection method 03 using a laser according to claim jllE1, where Ik is applied to a wiring part that is doped with impurities and is in a non-conducting state due to a high resistance part formed in a part of the polycrystalline & wiring in the low resistance part. , so that the laser beam covers the high resistance part of the wiring part and at least a part of the low resistance part on both sides, with a power of 1 or less, which is the lowest power density required to cut the polycrystalline & wiring with one pulse. The densely focused spot is relatively scanned, focused and irradiated from at least one low resistance part to the other low resistance part with a pitcher with a diameter of this spot or less several times to remove the above wiring part. 1. A wiring connection method using a laser, which connects wiring within a semiconductor device by changing the state from a conductive state to a conductive state.