JPS62199033A - Formation of thin-film - Google Patents

Abstract

PURPOSE:To arrange a conductive thin film flat over the minute unevenness of high aspect ratio by changing a distribution of flying directions of sputtering particles to a substrate according to a degree of unevenness of the surface of the substrate or intercepting the sputtering particles being incident from a direction which is largely inclined from a vertical direction of the substrate. CONSTITUTION:An SiO2 thin film 102 on an even Si substrate 101 is provided with minute holes. A shielding plate is arranged between the substrate and a sputtering target and the hole of the shielding plate is made narrow to prevent sputtering particles being incident from a direction which is largely inclined from a vertical line, thereby selecting bias sputtering condition. As a result, though a step coverage of shoulder parts of the hole is not good, there is no hangover of a deposited film from the shoulder parts and the film thickness which is almost the same as that of the surface of the substrate is formed also at the bottom of the hole. Next, the hole of the shielding plate is enlarged and the bias sputtering condition is selected. Then, an Al film 104 is deposited while making a film depositing rate at the bottom part larger than that on the hole stepped parts. By this constitution, a conductive film can be deposited with a high evenness of the surface without a shadow effect even the minute holes are of steep side planes and with high aspect ratio.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for forming a thin film, in particular a method for forming a thin film with good surface flatness on the surface of a substrate with steep sides and fine, high aspect ratio irregularities. It relates to a method of forming a .

(Prior Art) When performing wiring in a semiconductor device, contact holes are opened in an insulating film that protects the surface of a substrate 101, and
This is done by depositing a conductive film thereon. Due to advancements in exposure technology and dry etching technology, the formation of contact holes in recent LSIs, etc. has been reduced to a film thickness of 1 to 2 pm.
It is possible to make the insulating film 102 about 1 pm square. Such contact holes have steep sides and large steps, so if a conductor film is deposited using the conventional parallel plate sputtering method or vapor deposition method, as shown in Fig. Due to the shadow effect of the conductor film 201 itself, which has been deposited in large quantities, the step coverage is poor, the wiring is easily cut or thinned, and the manufacturing yield and reliability of the LSI are significantly lowered. In order to prevent these drawbacks, the side surfaces of minute contact holes are tapered and sloped so that the conductor film can be deposited uniformly. This is not a preferable improvement method because it will hinder the high integration of LSI.

Therefore, methods have been proposed for depositing a conductive film with good step coverage on steep, high aspect ratio grooves or contact holes, and one method uses a planetary-type substrate holder. There is a sputtering method. In this method, the flying direction of sputtered particles is made random to improve step coverage. It has been experimentally verified that the planetary sputtering method provides better step coverage than the parallel plate sputtering method. Furthermore, recently, a bias sputtering method that applies power to the substrate side during film formation and simultaneously performs film deposition and sputter etching on the substrate surface has been used to form thin films on substrates with uneven surfaces with good step coverage or It is also practiced to densely fill the inside of the contact hole and deposit it on a flat surface.

A.R. Neureuther (A.R.

IE Transactions on Electron Devices (I
EEE Trans, on ED,) 27.1449 (
1980). According to the report, width 21
It is stated that when a film is deposited by planetary sputtering on a groove of 1 m and an aspect ratio (depth: 1 width) of 065, the step coverage is extremely deteriorated due to the shadow effect. Furthermore, as shown by Mogami et al. in the 1985 Proceedings Second International Eye, EEBBLSI Multilevel Interconnection Conference (1985), even in thin film formation by bias sputtering, it is possible to reduce surface irregularities. When the aspect ratio becomes larger than a certain level, there is a problem in that, as in the case of normal sputtering, there remains a region in the recess where no thin film is deposited.

SUMMARY OF THE INVENTION An object of the present invention is to address the problems of conventional thin film forming methods as described above, and to provide a method for depositing a conductor deposited film with good flatness, particularly on fine irregularities with a high aspect ratio.

(Means for Solving the Problem) According to the present invention, at least the entrance of sputtered particles from other than the area where the sputter target is expected from the concave portion of the unevenness on the substrate surface is blocked, and the sputtered particles generated from the shoulder of the convex portion of the unevenness on the substrate surface are blocked. A first step of depositing a conductive thin film under bias sputtering conditions that suppresses the protrusion of the deposited film in the horizontal direction of the substrate, and a first step of depositing a conductive thin film under bias sputtering conditions that suppresses the protrusion of the deposited film in the horizontal direction of the substrate, and expanding the distribution of the flying direction of sputtered particles so that the film deposition rate of the conductive film on the concave portions of the unevenness is controlled. A conductive thin film is deposited under bias sputtering conditions that are higher than the film deposition rate of the conductive film on the convex portions of the unevenness,
A second step of making the thickness of the conductive thin film in the concave portion of the concave and convex portion approximately equal to the sum of the height of the convex portion of the concave and convex portion and the thickness of the conductive thin film on the convex portion of the concave and convex portion. A method for forming a thin film is obtained.

(Function) In the conventional thin film forming method using sputtering method or bias sputtering method, depending on the degree of surface unevenness,
When changing the distribution of sputtered particles in the flying direction relative to the substrate, or when the aspect ratio of irregularities on the substrate surface is large, it is possible to block sputtered particles that are incident from a direction perpendicular to the substrate (i.e., from a direction that is tilted). teeth,
It was not carried out.

In the present invention, irregularities on the surface of the substrate can be densely filled in based on the following principle. Conventionally, more sputtered particles came flying into the convex parts, but by blocking the entry of sputtered particles from areas other than the area where the sputter target is expected from the concave parts of the irregularities on the substrate surface, it is possible to reduce the distance between the convex parts and the concave parts of the irregularities. The number of sputtered particles flying from the target becomes equal, and the film deposition rate becomes equal between the convex portions and the concave portions of the unevenness. Furthermore, at the same time, the bias sputtering conditions are adjusted to suppress the protrusion of the deposited film from the shoulders of the convex portions of the unevenness in the horizontal direction of the substrate. Due to these two restrictions, the deposited film does not protrude from the shoulders of the convex portions of the unevenness, the shoulders of the convex portions are rounded, and a film is deposited with approximately the same thickness on the convex and concave portions of the unevenness. .

By doing this, the depth of the depressions and depressions will not change, but the corners of the shoulders will be rounded, so the width of the depressions will increase. Therefore, when a film is deposited to make the surface flat in the second step, no region remains where no deposit is deposited due to a shadow effect. In this way, it is possible to form a dense thin film with good surface flatness even on the surface of a substrate having irregularities with a high aspect ratio.

(Embodiment of the Invention) After depositing 102 to a thickness of about 1 pm using the CVD method, a film with a diameter of 11
A state in which a 1 m open hole is formed is shown. Next, Figure 1 (b
), a shielding plate is provided between the sputter target and the substrate, and the hole in the shielding plate is narrowed to block sputtered particles that enter the substrate from a direction that is greatly tilted from the vertical direction of the substrate. Bias sputtering conditions (argon gas pressure: 3 mTorr, distance between electrodes 295 mm, target side power density: 5.7 W/am2, bias voltage 300 V, target shape: circular, target size: 6 inches in diameter, shielding plate position 2 40 mm from the substrate surface
, hole diameter of shielding plate: 40mm) and aluminum film 10
Deposit 0.5 pm of 3. As a result, although the step coverage is poor, the deposited film does not protrude from the shoulder of the contact hole step, the shoulder part of the step is rounded, and the aluminum film inside the contact hole has the same thickness as the horizontal surface of the substrate. A film is deposited. Further, as shown in FIG. 1(c), the thickness of the conductive thin film at the bottom of the contact hole is approximately equal to the sum of the height of the contact hole step and the thickness of the conductive thin film above the contact hole step. Bias sputtering conditions (argon gas pressure of 3 mTorr) in which the hole in the shielding plate is enlarged and the film deposition rate of the conductor film at the bottom of the contact hole is higher than the film deposition rate of the conductor film on the step of the contact hole.
, interelectrode distance 95mm, target side power density 5.7W
/cm2, bias voltage knee 600V, diameter of the hole in the shielding plate: 90mm).

As a result, an aluminum film with a thickness of about 2 pm is deposited inside the contact hole, an aluminum film with a thickness of about 1 pm is deposited on the flat surface above the step of the contact hole, and the surface of the aluminum film on the silicon oxide film with the contact hole is almost completely covered. Become flat.

Although an aluminum film was deposited in the above embodiments, there is no need to limit it to this, and other metals such as molybdenum, polycrystalline silicon doped with impurities, alloys such as silicide, etc. can also be used.

In the embodiment described above, a shielding plate with one hole was used, but a shielding plate with a plurality of holes may also be used. The plurality of holes improves the film uniformity of the deposited film on the substrate.

(Effects of the Invention) As explained above, according to the present invention, even in a fine contact hole with a steep side surface and a high aspect ratio,
The conductor film can be deposited with good surface flatness without producing a shadow effect. As a result, it is possible to avoid wiring breakage and poor contact in a multilayer wiring structure of 2 to 3 layers.
When used for SI, reliability and yield can be dramatically improved.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are schematic cross-sectional views for explaining an embodiment of the method of the present invention, and FIG. 2 shows an embodiment of film deposition by a conventional parallel plate sputtering method. FIG. 101...Silicon substrate 102...Silicon oxide film 103.104...Aluminum film 201
...Deposited conductor film Fig. 1 (b) (C1 Kabuto 2 Fig. 2)

Claims (1)

[Claims] Bias sputtering that blocks the entry of sputtered particles from areas other than the area where the sputter target is expected from at least the concave portions of the substrate surface irregularities, and suppresses the protrusion of the deposited film from the shoulders of the convex portions of the substrate surface in the horizontal direction of the substrate. a first step of depositing a conductive thin film under the conditions, and a bias that widens the distribution of sputtered particles in the flying direction so that the film deposition rate of the conductive film on the concave portions of the concave and convex portions is higher than the film deposition rate of the conductive film on the convex portions of the concave and convex portions; A second method in which a conductive thin film is deposited under sputtering conditions, and the thickness of the conductive thin film in the concave portions of the concave and convex portions is approximately equal to the sum of the height of the convex portions of the concave and convex portions and the thickness of the conductive thin film on the convex portions of the concave and convex portions. A method for forming a thin film, comprising the steps of: