GB2213167A

GB2213167A - Deposition of materials on to substrates

Info

Publication number: GB2213167A
Application number: GB8828367A
Authority: GB
Inventors: Sunil Pandharinath Talim
Original assignee: National Research Development Corp UK
Current assignee: National Research Development Corp UK
Priority date: 1987-12-04
Filing date: 1988-12-05
Publication date: 1989-08-09
Also published as: JPH03502213A; WO1989005361A1; GB8828367D0; EP0396583A1; GB8728399D0

Abstract

A localised charge pattern is written on the surface of an insulating substrate (1) using an electron gun (3, 4, 5, 6). Subsequently, a metallic layer is preferentially deposited on the charged regions by means of a vaporising filament (7).

Description

DEPOSITION OF MATERIALS ON TO SUBSTRATES This invention relates to the deposition of materials on to substrates and, in particular, to the preferential, localised deposition of materials on to insulators and semiconductors.

Driven by demand for submicron integrated circuits, optical engineers have been actively developing new photoresists, short wavelength printing methods and mask production using electron or ion beam and X-rays. This technology is also used for photolithographic optics, data storage and cosmetic applications. A typical modern lithographic process employs a fine mask produced say by electron beam machining which is imaged on a high resolution photoresist using deep ultra-violet radiation. Tight tolerances and the reproducibility demanded in exacting applications, however, continue to pose problems.

We have devised a method of localised deposition of materials on to insulating and semi conducting substrates. This method involves writing an artwork directly on to an insulating substrate using electrons or ions and depositing a metallic or a dielectric film by an indirect vacuum deposition (where the substrate is shielded from the direct stream of vapour) on this pattern without any masking or additional treatment to the substrate.

Studies carried out on the nucleation of low energy vapours in vacuum deposition of thin films on dielectric substrates have shown that nucleation occurs at charged sites on the substrate.

It was also observed that in the vapour phase some compounds dissociate (and elements ionise) and therefore show greater attraction to charged sites and the film builds up mainly on the charged region producing a sharp edge. Preliminary investigations carried out with vapours of zinc and zinc sulphide indicate that the above procedure can be applied for an efficient writing process which is suitable for many photolithographic applications.

The effectiveness of one-stage operation was established by using an argon atom beam gun and zinc sulphide. Typically a film about O.4#m thick of zinc sulphide was produced on a glass substrates in about one minute. Such films were found to be very adherent and hard. By using oxygen or nitrogen ion beams, either oxide or nitride films can be produced in a similar manner.

According to the present invention, there is provided a method of deposition of material on to a non-conducting substrate comprising writing a pattern of electrically-charged particles to create charged regions on the substrate and preferentially depositing said material on to said charged regions.

Tne charged regions ma. be created directly or by charging the substrate uniformly and subsequently discharging it locally by irradiation.

An embodiment of the invention will now be described, by way of examp e, with reference to the accompanying drains, in which: Figure 1 is a diagrammatic representation of apparatus stable for depositing films using the method of the invention, Figures 2 to 8 are micrographs showing films deposited in accordance with tne invention, and Figure 9 is a trace of a stylus instrument scan of the film cf Figure E.

Referring now to the drawing, a glass substrate 1 is mounted within a vacuum chamber 2. A charge pattern is written on the surface of the substrate using an electron gun comprising a filament 3, modulating grid 4, accelerating electrode 5 and deflection electrodes 6. Subsequently, a layer of zinc is preferentially deposited on the charged regions by means of an vaporising filament 7.

In a further embodiment, using two simple metallic masks, charged patterns written on glass microscope slides with thermal electrons were coated with indirect films of zinc and zinc sulphide. Letters NPL at a magnification of approximately one, visible as a sharp bright pattern of metallic zinc (Figure 2) show that the electric field generated by the charge can be adjusted to prevent deposition on uncharged area. The micrograph (Figure 3) at a magnification of 32 indicates that good masking can indeed produce a sharp step. Measurements made using a Rank Taylor Hobson Talystep instrument showed that the film was about 120nm thick and therefore opaque to visible light.A "negative" of a thinner stainless steel mask of a fine hexagonal pattern with only 0.3mm wide bars was produced with a zinc sulphide film (Figure 4) where the sharper horizontal bars are due to better masking.

Application of this method to a large area is demonstrated by the photograph in fig (1). It shows a zinc metal film on a pattern in the form of the letters NPL approximately 75x25mm written with electrons on a glass substrate. In initial experiments the substrate was flooded, with electrons and a pattern produced by shadowing through a mask. A film of zinc, approximately 120mm thick was deposited separately by indirect evaporation. The micrograph in Figure 6 demonstrates that the simple shadowing procedure can also be used to write very fine patterns. In these experiments a thin copper mask was used. It had four 2mm diameter and lOOpm wide rings with four concentric pin holes of 5, 10, 15 and 2Opm diameters respectively.This patter was written on silica substrates using thermal electrons and indirect films of zinc sulphide evaporated in a separate operation. It is evident from the photograph that the condensation has occurred exclusively on the charged area. It was noted that lack of collimation of the electron beam and the separation between the mask and the substrate introduce some loss of definition.

Natural oxidation of metals can provided adequate insulation to be able to carry out such a charged writing. This was established by writing fine charge patterns on chargealuminium and silicon substrates. The micrograph in Figure 7 shows a sharp pattern of a grid where the finest lines are about l5#m wide and about 50nm thinner than the surrounding area. It was written with a zinc sulphide film on a silicon substrate.

To produce a submicron size patterns focused charged beams are employed for the writing. Fine charged lines have been written on silica substrates in a scanning electron microscope employing various accelerating voltages and different spot size.

The width and the thickness of the films subsequently deposited showed close correspondence to the writing conditions. One of the zinc sulpnide lines produced in this way is shown in Figure 8. it was about 5#r wide and the scan of this line using a Ta '.yst--'# srs;us measuring instrument in Figure 9 showed that it was about 44nm thick and had a sharp edge. Some lack of definition may be due to spherical aberration in the electron optics and the slope of the Talystep trace may have been increased by the shape of the stylus.

It will be apparent from the above results that the process can be applied to large or small and metal or dielectric substrates. It is also demonstrated that either metallic or insulating films of a few micrometer to several millimetre wide features can be produced.

In many applications thickness variation of the same film is often required. Such a variation can be achieved by direct depositîcb of a film on the charged writing. The additional attractive force of the charge produces a thicker film on the art work. The micrograph at a magnification of 80 (Figure 5) shows a sharp pattern due to colour changes which are introduced by thickness variation of a zinc sulphide film on a charged glass substrate; the film on the charged region was about 50nm thicker.

The method described above finds wide application to: Study of optical and electrical properties of materials in vapour and solid phase.

Chip architecture.

Multiple writing head.

The charge enhanced deposition will be particularly useful for the manufacture of integrated electronic and integrated optic chips.

As charged writing and subsequent deposition of a thin film is carried out in vacuo this procedure is particularly applicable to automation. The very short wavelength of the electrons allows writing of very fine patterns at high packing densities and their low energy provides high definition with negligible substrate damage. Techniques currently used for ion beam machining, with some modifications, are suitable for the writing operation.

Subsequent deposition of a film on such a pattern is also useful for exacting applications such as line width standards, mask production and as a resist layer. Oxygen and nitrogen ion or atom beams can be employed for writing oxide and nitride patterns. Electron beam energy, density, diameter and energy distribution tailored to a specific application can be applied for the production of blazed, sinusoidal or square wave diffraction gratings, zone plates or "Moth Eye" anti-reflection coatings in hard dielectric films. Such hard master copies are ideal for replication. As the films can be transparent or opaque, both phase and amplitude diffraction optics can be fabricated. The process is particularly suitable for writing on plastics as a discharge treatment of plastic substrates improves the adhesion of a subsequently applied film.

Although the invention has been described with reference to insulator or semiconducting subtrates, it is also applicable to conducting substrates with an insulating layer on the surface which holds the electrical charge during the deposition process.

It has been demonstrated that the technique is applicable to aluminium and silicon with a surface oxide layer.

Claims

1. A method of deposition of material on to a non-conducting substrate comprising writing a pattern of electrically-charged particles to create charged regions on the substrate and preferentially depositing said material on to said charged regions.

2. A method of deposition of material on to a non-conducting substrate as claimed in claim 1 wherein the charged regions are created directly.

3. A method of deposition of material on to a non-conducting substrate as claimed in claim 1 wherein the charged regions are created by charging the substrate uniformly and subsequently discharging it locally by irradiation.

4. A method of deposition of material on to a non-conducting substrate as claimed in claim 2 wherein a charge pattern is written on the surface of the substrate using an electron gun.

5. A method of deposition of material on to a non-conducting substrate as claimed in claim 4 wherein a conducting layer preferentially deposited on the charged regions by means of an vaporising filament.

6. A method of deposition of material on to a non-conducting substrate as claimed in either claim 4 or 5 wherein the charge pattern is written using a collimated electron beam.

7. A method of deposition of material on to a non-conducting substrate as claimed in any one of the preceding claims including the step of forming an insulating layer on a conducting or semi-conducting substrate.

8. A method of deposition of material on to a non-conducting substrate as claimed in any one of the preceding claims wherein a film of increased thickness is preferentially deposited by deposition on to a charged region of the substrate.

9. A method of deposition of material on to a non-conducting substrate as claimed in claim 2 wherein the electron beam is focused on the substrate.

10. A method of deposition of material on to a non-conducting substrate as claimed in any one of the preceding claims using a multiple writing head.

11. A method of deposition of material on to a non-conducting substrate as claimed in claim 7 wherein an oxygen beam is employed to form an oxide layer on the substrate.

12. A method of deposition of material on to a non-conducting substrate as claimed in claim 7 wherein a nitrogen beam is employed to form a nitride layer on the substrate.

13. An optical component produced by a method as claimed in any one of the preceding claims 1 to 12.

14. A replication master prduced by a method as claimed in any one of the preceding claims 1 to 12.

15. An integrated circuit produced by a method as claimed in any one of the preceding claims 1 to 12.

16. A method of depostion of material on to a non-conducting substrate substantially as herein described with reference to and as shown in the accompanying drawings.

17. A device produced by the method of claim 16.