JPH0666313B2 - Semiconductor device manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing a multi-level metallization structure for semiconductor devices, particularly integrated circuits. In particular, the present invention relates to a method of making a multi-level metallization structure that uses aluminum to form good ohmic contacts between levels.

[Description of Conventional Method] In the manufacture of semiconductor integrated circuits, there is a tendency to increase the number of components per unit area of a circuit chip in order to reduce the cost per circuit function. This increase is obtained by reducing the dimensions of the components themselves and / or the spacing between the components. However, one of the factors limiting the reduction in size and spacing is the area required for the metal connections used to connect the various components of the desired circuit.

One way to overcome the problem of metal connections is to use a multi-level metallization scheme. The multi-level metallization scheme forms openings through the insulating layer on the substrate of the device to some components within the substrate. Depositing a first metal layer on the insulating layer and in the opening, defining the first metal layer to form part of a total metal connection system, and defining the first metal layer. A second layer of insulating material is deposited thereon and an opening is formed through the second insulating layer. Some of the apertures may completely penetrate the insulating layer to reach some of the components in the substrate, while some simply penetrate the second insulating layer to reach the defined first metal layer. It's just A second metal layer is deposited on the second insulating layer and in the contact openings, which is defined to form the remainder of the total connection system, and the second metal layer thus defined is deposited. It connects to some of the components in the substrate and to the defined first metal layer. Additional metal layers can be used if the circuit is sufficiently complex and it is required.

The metal commonly used for metallization in integrated circuits is aluminum or aluminum with a small amount of silicon because of its high conductivity, ease of deposition and relatively low cost. However, the problem with aluminum is that a thin film of aluminum oxide forms on the surface of aluminum when exposed to air immediately after deposition. This aluminum oxide is not a major problem when aluminum is used for single level metallization, but is problematic for multilevel metallization.
This oxide layer provides an insulating layer between the two metallization layers which produces high resistance where they contact each other. Attempts have been made to reduce the contact area to make the high contact resistance as low as possible by making the area of the openings in the insulating layer between the two metallization layers larger than the line width of the defined metallization layer. About 40
The resistance is further reduced when heated to 0 ° C to destroy the aluminum oxide and sinter the two layers, but this does not completely remove the oxide and is found to be higher than without the oxide. It is connected. Further, when the dielectric layer is overetched to form an excessively large aperture hole, an undercut of the dielectric layer occurs, and the edge of the undercut deteriorates the step coverage of the next deposited layer.

[Outline of the present invention]

The semiconductor device comprises a substrate having a first layer of insulating material on its surface,
There is a first conductive layer on the first insulating layer, and there is a second layer of insulating material on the first conductive layer, and the second insulating layer has through holes. A second layer is formed on the second insulating layer.
Of conductive layers through the apertures and contacting the first conductive layer. The first conductive layer is aluminum containing 3% or less of silicon, and the second conductive layer is aluminum containing a smaller amount of silicon than the first conductive layer. When manufacturing this semiconductor device, a first conductive layer is deposited on the first insulating layer, and a second insulating layer is deposited on the first conductive layer.
After forming an opening in the second insulating layer, the exposed portion of the first conductive layer is etched with an etching liquid. The etching liquid removes aluminum on the exposed surface but is contained in the aluminum-silicon conductive layer. It leaves the deposited silicon particles. A second conductive layer is then deposited and the second conductive layer is heat annealed to the first conductive layer at the interface with the first conductive layer in the aperture.

[Detailed description of the preferred embodiment]

FIG. 1 shows an entire semiconductor device 10 embodying the present invention. The semiconductor device 10 includes a substrate 12 of a single crystal semiconductor material, such as silicon, having a major surface 14, along which a variety of active and passive devices such as transistors, diodes, resistors, etc. are located along the surface 14. Then, these are electrically connected to each other to form a required circuit.
These devices may have different conductivity types than the substrate 12, for example, in the regions 16 and 18, and may have different specific resistances of the same conductivity type. On the surface of the substrate 12 is a first layer 20 of insulating material, such as silicon dioxide, on which the area 1
There is a pair of openings 22, 24 leading to 6, 18. First insulating layer 2
A part of 0 has a first conductive layer 26 which enters the opening 22 and contacts the region 16. The first conductive layer 26 is aluminum containing silicon, and its silicon content is preferably about 3% or less.

The first conductive layer 26 and the first insulating layer 20 not covered by the first conductive layer 26.
Is covered with the second insulating layer 28. The second insulating layer 28 can be an inorganic material such as silicon dioxide or silicon nitride or an organic material such as polyimide. Two openings 30, 32 also penetrate the second insulating layer 28, which openings 32 reach the area 18 of the first insulating layer 20.
Consistent with 24. A portion of the second insulating layer 28 has a second conductive layer 34 that contacts the first conductive layer 26 through the apertures 30 and contacts the region 18 through the matching apertures 32, 24. ing. The second conductive layer 34 is aluminum containing a smaller amount of silicon than the first conductive layer 26. The conductive layers 26 and 34 are defined and serve as connection conductors, and connect various devices in the substrate 12, such as the regions 16 and 18, to each other and to the terminal pad of the semiconductor device 10. As will be described in more detail below, the second conductive layer 34 forms a sintered interface with the first conductive layer 26 and adjoins the interface with a greater amount of silicon than other portions of the second conductive layer 34. It has a region containing. This allows the two conductive layers 26,
Low resistance contact is provided between 28.

When making semiconductor device 10 using the method of the present invention, the substrate is prepared using standard semiconductor techniques such as ion implantation or diffusion.
After forming the regions 16 and 18 in 12, the first insulating layer 20 is formed on the surface 14. This first insulating layer 20, if it is silicon dioxide, can be grown by exposing the surface 14 to oxygen or water vapor at about 800-1200 ° C. Next, an opening 22 is formed in the first insulating layer 20. This is done by depositing photoresist on the entire surface of the first insulating layer 20 and then forming the pattern where the openings 22 should be formed using standard photolithographic techniques, exposing the first insulating layer 20. This can be done by removing the parts with a suitable etching solution such as buffered hydrofluoric acid for silicon dioxide.

Next, the first conductive layer 26 is formed. This is done by depositing a layer of silicon-containing aluminum on the entire surface of first insulating layer 20 and in openings 22 by any standard deposition method such as vacuum evaporation or sputtering. After forming a photoresist pattern layer by a standard photoengraving method on a portion of the silicon-containing aluminum layer where the first conductive layer 26 is to be formed,
The exposed portion of the silicon-containing aluminum layer is removed by plasma etching or a suitable etching method such as wet chemical etching using an etching solution of about 50 ° C. consisting of 20 parts H ₂ PO ₄ and HNO ₃ 1 blowing.

A second insulating layer 28 is then deposited over the exposed portions of the first conductive layer 26 and the first insulating layer 20, as shown in FIG. When the second insulating layer is an inorganic material, such as silicon dioxide or silicon nitride, the device is then deposited using standard chemical vapor deposition.
It can be deposited by exposing the insulating layer to a gas containing an element and reacting the gas by heating to deposit a specific material. When the second insulating layer 28 is an organic material such as polyimide, it can be applied or cured by coating or spinning. Next, in order to form the openings 30 and 32 in the second insulating layer 28, a photoresist layer is deposited on the entire surface thereof, and a pattern is formed at the place where the opening is formed by using a standard photoengraving method. Then, the exposed portion is removed by an etching liquid suitable for the material used for the second insulating layer 28. The opening 24 of the first insulating layer 20 can be formed by etching the surface of the first insulating layer 20 exposed at the bottom of the opening 32 of the second insulating layer 28. Second insulating layer 28
If the material of the first insulating layer 20 is the same as that of the first insulating layer 20, the first insulating layer 2 is automatically opened by etching when forming the opening 32.
24 is formed, but when the material of the second insulating layer 28 is different from that of the first insulating layer 20, after forming the opening 32, the opening 24 is formed by using an appropriate etching method.

Next, an etching solution is applied to the surface of the first conductive layer 26 exposed at the bottom of the opening 30 of the second insulating layer 28 so as to dissolve aluminum but not silicon. This makes it the fourth
As shown in the figure, the aluminum portion of the exposed portion is dissolved and removed, and the silicon particles 36 remain protruding from the exposed surface. At this time, it is preferable that about 1000 Å of aluminum is removed from the exposed surface to obtain a rough surface by the protruding silicon particles 36.
Etching solutions that appear to be suitable for this purpose include H ₃ PO ₄ and HNO
Mixture of ₃ , buffered hydrofluoric acid, dilute hydrofluoric acid, and H ₂ O, HF, CuSO ₄
There is a solution of. Mixture containing CuSO _4, the copper is plated onto the silicon particles exposed, it is Hunts extremely performance is good to limit the etching of the aluminum depending on the size and density of the silicon particles. This copper plating surface is next
When immersed in HNO ₃ , the copper is removed to expose the surface with dense silicon particles. During this etching step, all aluminum oxide is removed from the exposed surface and at the same time a rough surface is obtained.

Then, the entire surface of the second insulating layer 28 and the holes 30, 32, and 24
A layer of aluminum containing a smaller amount of silicon than that of the copper electrode layer 26 is deposited, and after the photoresist is deposited on this metal layer, this is removed by leaving only the necessary portion, and the exposed portion is removed by a suitable etching method. The second conductive layer 34 is formed by removing.

The device 10 is then heated to about 400 ° C. to form the second conductive layer 34 first.
The conductive layer 26 is sintered. The first during this sintering
The silicon particles 36 of the conductive layer 26 are dissolved in the second conductive layer, and additional silicon diffuses from the first conductive layer 26 to the second conductive layer 34 having a lower silicon content. As a result, the aluminum / silicon alloy fills the place where the silicon was formed before the interface between the two conductive layers, and the silicon content in the second conductive layer 34 contacting the interface is changed as shown in FIG. More regions 34a are formed than the rest of layer 34.
The sintering of the two conductive layers 26, 34 provides good electrical contact between them, and the diffusion of silicon through the interface destroys any oxide formed on the exposed aluminum surface, thus Since the top surface of the conductive layer 26 contains a high density of silicon particles, the exposed and oxidized surface of aluminum is significantly reduced. All of these conditions act to form a good low resistance contact, which resistance contact is obtained in a very small area contact area.

The following example is not an example of the present invention because aluminum of the second conductive layer does not contain silicon, but it is useful for understanding the effect of the semiconductor device manufactured by the present invention.

Example 1 Each device was manufactured as follows, and a group of test pattern devices was prepared. First, a single crystal silicon substrate is heated to about 1100 ° C. in water vapor to form a silicon dioxide layer on the surface thereof, and a first metal layer is deposited on the silicon dioxide layer by spastering. Define this 32
Forty-five μ × 70μ metal island regions were formed. Then, after depositing a layer of silica glass containing 3% by weight of neighbors on the substrate and the first metal islands by chemical vapor deposition at atmospheric pressure,
90 apertures of about 10 μ square were formed in this adjacent silica glass using buffered hydrofluoric acid to reach the first metal island region. Two holes were formed in each metal island region, and the holes were arranged so as to have a uniform interval both inside and between the island regions. The etching of the aperture was long enough to etch the surface of the first metal island region at its bottom.
A second metal layer was then deposited by sputtering on the glass layer and into the apertures, making contact with the first island regions. Next, the second metal layer is defined to form a plurality of island-shaped regions each having a size of 32 μ × 70 μ, and each island-shaped region extends from one opening of the first island-shaped region to the adjacent first island-shaped region. It was designed to extend into one of the openings in the area. Therefore, this second island region is
That is, the first island-shaped regions including the contact with the island-shaped regions are electrically connected in series. Next, this apparatus was heated at 450 ° C. for 4 hours to sinter the second island-shaped region into the first island-shaped region.

Aluminum was used for the second metal layer forming the second island region in all devices, but the thickness was 1 μ in some devices and 2 μ in others. The first metal layer was aluminum containing 1% silicon in some devices and aluminum containing 2% silicon in others.

For each device, measure the resistance of the islands connected in series and divide the measured value by the number 90 of contacts between the first and second islands to obtain the contact resistance at the interface of both islands plus each contact. The average resistance of the metal line between the points was determined. This average resistance for each device is shown in Table 1.

A group of test pattern devices was made in the same manner as in Example 1,
The aperture of the adjacent silica glass was about 15 μ square. The average resistance for each device is shown in Table 2.

A group of test pattern devices was made in the same manner as in Example 1,
The opening of the adjacent silica glass was about 20 μ square. The average resistance for each device is shown in Table 3.

From the above tables, it can be seen that the device using silicon-containing aluminum for the first metal layer has a lower contact resistance than the device using both metal layers made of aluminum. In addition, the higher the silicon content of the first metal layer is, the lower the contact resistance is.
It is also understood that the thicker the metal layer of, the lower the contact resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device embodying the present invention, and FIG.
5 to 5 are sectional views showing the steps of the method of the present invention for producing the semiconductor device shown in FIG. 10 ... Semiconductor device, 12 ... Substrate, 14 ... Substrate surface, 20 ...
... first insulating layer, 26 ... first conductive layer, 28 ... second insulating layer, 30 ... holes, 34 ... second conductive layer.

Claims (3)

[Claims] 1. A step of forming a first metallization layer of aluminum containing 3% or less of silicon on a surface of a substrate, and a step of forming a layer of an insulating material on the first metallization layer. Forming a hole through the insulating layer to the first metallization layer in such a way that a portion of the aluminum on the surface of the first metallization layer is removed and a portion of the silicon particles is exposed. And contacting a second metallization layer of aluminum containing a smaller amount of silicon contained in the first metallization layer on the insulating layer and in the apertures. And heating the metallization layer so that the two metallization layers sinter at the joints of the two in the openings in the insulating layer and from the first metallization layer. D. A portion of silicon diffusing into the second metallization layer; A method of forming a structure. 2. The method of claim 1, wherein the surface of the first metallization layer within the apertures in the insulating layer is treated to form a first metallization layer prior to forming the second metallization layer. A method of removing a part of aluminum on the surface of the metallized layer and exposing a part of silicon particles. 3. The method of claim 2 wherein the first metallization layer is treated by exposing it to an etchant that removes aluminum but not silicon.