METHOD AND SYSTEM FOR DEPOSITING A P-TYPE OXIDE LAYER ON A SUBSTRATE

Abstract

A method and system for depositing an atomic layer on a substrate. The method performs one or more method cycles to form a p-type oxide layer, wherein a method cycle includes performing successively the steps of: exposing the substrate to a Sn(IV) or Cu(II) precursor gas, exposing the substrate to an oxygen donor gas, wherein prior to and/or after exposing the substrate to the oxygen donor gas, hydrogen radicals are exposed to the substrate.

Claims

1. A method for depositing an atomic layer on a substrate, the method comprising performing one or more method cycles for forming a semiconductor p-type oxide layer on the substrate, wherein a method cycle includes performing successively the following: exposing the substrate to a Sn(IV) or a Cu (II) precursor gas so as to deposit an atomic layer comprising Sn(IV) or respectively Cu(II) on the substrate; and exposing the substrate to an oxygen donor gas, wherein, in association with the method cycle, hydrogen radicals are exposed to the substrate prior to and/or after the exposing the substrate to the oxygen donor gas so as to provide reduction of Sn(IV) to Sn(II) or Sn(0), or respectively reduction of Cu(II) to Cu(I) or Cu(0).

2. The method according to claim 1, wherein hydrogen radicals are provided by a H.sub.2 containing plasma.

3. The method according to claim 1, wherein a non-oxidizing oxygen donor gas is used, in accordance with the method cycle where the H.sub.2 plasma is exposed prior to exposing the substrate to the oxygen donor gas.

4. The method according to claim 1, further including converting Sn(0) or Cu(0) to Sn(II) or Cu(I), respectively.

5. The method according to claim 1, wherein both the exposing the substrate to the oxygen donor gas and the exposing the hydrogen radicals to the substrate are performed at a temperature of about 250° C. or lower.

6. The method according to claim 5, wherein the exposing the substrate to the oxygen donor gas and exposing the hydrogen radicals to the substrate is performed at a temperature of between 100° C. and 250° C.

7. The method according to claim 1, wherein the forming the semiconductor p-type oxide layer on the substrate is performed under a pressure between 130 Pa and 650 kPa.

8. The method according to any one of the preceding claim 1, further comprising subjecting the atomic layer on the substrate including the p-type oxide layer to an annealing at a temperature between 100° C. and 250° C.

9. The method according to claim 8, wherein the annealing is carried out for a period of time having a duration within a range from 30 minutes to 2 hours.

10. The method according to claim 1, wherein the oxygen donor precursor gas is selected from the group consisting of: oxygen (O.sub.2), ozone (O.sub.3), water (H.sub.2O), hydrogen peroxide (H.sub.2O.sub.2), carbon dioxide (CO.sub.2), carbon monoxide (CO), methanol (CH.sub.3OH), ethanol (C.sub.2H.sub.6OH), isopropyl alcohol (C.sub.3H.sub.7OH), nitric oxide (NO), nitrous oxide (N.sub.20) and combinations of two or more of the afore-mentioned compounds.

11. The method according to claim 1, wherein a purging step with an inert gas is carried out after one or more instances of exposing the substrate to the Sn(IV) or the Cu(II) compound, exposing the substrate to an oxygen donor gas or exposing the substrate to hydrogen radicals.

12. A system for depositing an atomic layer on a substrate, wherein the system is configured to perform one or more method cycles for forming a p-type oxide layer, wherein the system comprises a deposition chamber with a substrate holder arranged therein, the substrate holder being configured to hold the substrate, wherein the deposition chamber includes at least one gas supply member through which gas can be supplied to and/or removed from the deposition chamber, wherein the system further includes a controller arranged for controlling the system to successively carrying out in a method cycle the following: supplying, through the at least one gas supply member, a Sn(IV) or a Cu(II) precursor gas to the substrate; supplying, through the at least one gas supply member, an oxygen donor precursor gas to the substrate, wherein hydrogen radicals are supplied to the substrate prior to and/or after exposing the substrate to the oxygen donor precursor gas so as to provide reduction of Sn(IV) to Sn(II) or Sn(0), respectively reduction of Cu(II) to Cu(I) or Cu(0).

13. A method for forming a semiconductor device by depositing an atomic layer on a substrate by performing a plurality of method cycles according to claim 1.

14. A semiconductor device to which a p-type oxide layer is applied, obtained by performing the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0047] The invention will further be elucidated on the basis of exemplary embodiments which are represented in a drawing. The exemplary embodiments are given by way of non-limitative illustration. It is noted that the figures are only schematic representations of embodiments of the invention that are given by way of non-limiting example.

[0048] In the drawing:

[0049] FIG. 1 shows a schematic diagram of a method cycle;

[0050] FIG. 2 shows a schematic diagram of a method cycle;

[0051] FIG. 3 shows a schematic diagram of a method cycle;

[0052] FIG. 4 shows a schematic diagram of a method cycle;

[0053] FIG. 5 shows a schematic diagram of a method cycle;

[0054] FIG. 6 shows a schematic diagram of a method cycle; and

[0055] FIG. 7 shows a schematic diagram of a method.

DETAILED DESCRIPTION

[0056] FIG. 1 shows a schematic diagram of a method cycle 1 in a method for depositing an atomic layer on a substrate 3. The method performs one or more method cycles to form a semiconductor p-type oxide layer on the substrate 3. The description hereafter will concentrate on the formation of a Sn oxide layer on the substrate. It shall however be clear to the skilled person that the given description is also valid for the deposition of a Cu oxide layer. A method cycle includes performing successively the steps of: exposing the substrate to a Sn(IV) precursor gas 5, exposing the substrate to an oxygen donor 7. Prior to exposing the substrate 3 to the oxygen donor 7, hydrogen radicals 9 are exposed to the substrate such as to provide reduction of Sn(IV) to Sn(II). By means of the hydrogen radicals 9 exposure, the valence of tin can be reduced from 4 to 2.

[0057] Between the atomic layer deposition steps in the method cycle, purging is carried out using N.sub.2 gas 11. Advantageously, the N.sub.2 gas will not react with the formed layer on the substrate. Other inert gasses may also be used for purging, for example helium, argon or neon or any other gas that is inert in the conditions prevailing in the system.

[0058] The p-type oxide layer can be fabricated using an atomic layer deposition (ALD) process. Using a Sn(IV) precursor in an ALD process, a mono-oxide tin layer can be obtained. Using a Cu(II) precursor in an ALD process, a mono-oxide copper layer can be obtained. Cu(II)O and Cu2(I)O are both mono-oxides. ALD allows i.a. better control over the thickness than other methods such as sputtering, such that an adequate homogenous layer thickness can be obtained. As a result, a lot of control over the properties of the deposited layer can be obtained.

[0059] Most tin precursors are Sn(IV) precursors. However, in the prior art Sn(II) precursors were used for obtaining a tin monoxide layer with ALD, because Sn(IV) precursors would have created a tin dioxide layer. According to the invention, a tin monoxide layer (Sn(II)) is obtained with (spatial) ALD using an Sn(IV), by using an additional step in which hydrogen radicals are exposed to the formed layer after the Sn(IV) precursor is exposed to the substrate. The hydrogen radicals can be obtained by employing a H.sub.2 plasma. This step can be performed prior to or after the exposure of the formed layer on the substrate to an oxygen donor.

[0060] FIG. 2 shows a schematic diagram of a method cycle 1 in a method for depositing an atomic layer on a substrate 3. Similar to the example shown in FIG. 1, the method performs one or more method cycles to form a semiconductor p-type oxide layer on the substrate 3. A method cycle includes performing successively the steps of: exposing the substrate to a Sn(IV) precursor gas 5, exposing the substrate to an oxygen donor 7. After exposure of the substrate 3 to the oxygen donor 7, hydrogen radicals 9 are exposed to the substrate such as to provide reduction of Sn(IV) to Sn(II). Also in this case, between the atomic layer deposition steps in the method cycle, purging is carried out using N.sub.2 gas 11.

[0061] The sequence of the hydrogen exposure step and the oxygen donor step in a method cycle can thus be changed (cf. examples of FIG. 1 and FIG. 2). The oxygen donor step can depend on the sequence of steps. As discussed above, it may be desired to employ a non-oxidizing oxygen donor if the H.sub.2 plasma is exposed prior to exposure to the oxygen donor gas. Other variant sequences are also possible. For example, it will be appreciated that optionally, the hydrogen exposure step is employed prior to and after the oxygen donor step in the method cycle.

[0062] Though experimental results show that exposing hydrogen radicals to the substrate prior to or after exposing the substrate to the oxygen donor gas in both cases leads to a thin film containing Sn(II)O, as a result of the reduction of Sn(IV) to Sn(II), the first case (H.sub.2-plasma provided between Sn(IV)-precursor and oxygen precursor) may tend to give better results at least in some cases. The deposition process can be optimized. Experimental results show that tin oxide films with at least 60% Sn(II)O at the surface can be deposited. The formation of metallic tin can be substantially prevented.

[0063] P-type conductivity has been demonstrated in these films with a measured Hall mobility of up to 8 cm.sup.2/Vs and a carrier density of ˜1016 cm.sup.−3.

[0064] FIG. 3-6 show a schematic diagram of method cycles 1. In FIG. 3, a SnO process is shown including a Sn precursor exposure step, a H.sub.2 plasma exposure step, and a H2O exposure step. In FIG. 4 a SnO process is shown including a Sn precursor exposure, a H2O exposure step, and a H.sub.2 plasma exposure step. In FIG. 5 a Cu2O process is illustrated, including a Cu precursor exposure step, a H.sub.2 plasma exposure step, and H2O exposure step. In FIG. 6 a Cu2O process step is shown, including a Cu precursor exposure step, a H2O exposure step, and a H.sub.2 plasma exposure step.

[0065] FIG. 7 shows a schematic diagram of a method 1000 for depositing an atomic layer on a substrate, the method performing one or more method cycles to form a semiconductor p-type oxide layer on the substrate, wherein a method cycle includes successive steps. In a first step 1001, a Sn(IV) or Cu(II) precursor gas is exposed to the substrate. In a second step 1002, an oxygen donor gas is exposed to the substrate. In a third step 1003, hydrogen radicals are exposed to the substrate prior to and/or after exposing the substrate to the oxygen donor gas such as to provide reduction of Sn(IV) to Sn(II) or Sn(0), or reduction of Cu(II) to Cu(I) or Cu(O), respectively.

[0066] The present inventors have recognized that a key to improving throughput and upscaling for ALD processes, lies in the use of Sn(IV) precursors for forming a thin film of Sn(II)O onto the substrate, wherein an exposure to hydrogen radicals is used for reduction of Sn(IV) to Sn(II) of the Sn-oxide compound of the formed layer on the substrate.

[0067] ALD is very advantageous for forming thin layers on a semiconductor substrate. Instead of using a Sn(II) precursor, gas, a Sn(IV) precursor gas can be used. Sn(IV) is more preferable because it i.a. provides a better scalability and moreover is more common than Sn(II). In order to obtain a p-type oxide layer starting from Sn(IV), an additional step is used in which hydrogen radicals are supplied towards the surface of the substrate. Hereby the Sn(IV) can be reduced to Sn(II). This additional step can be used either before the oxidant precursor is added or after the oxidant precursor is added. In both cases, a resultant p-type Sn(II) oxide layer will advantageously be obtained. A combination is also possible, wherein both prior to and after the oxygen donor is exposed, the hydrogen radicals are exposed to the formed layer on the substrate.

[0068] Herein, the invention is described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications, variations, alternatives and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged and understood to fall within the framework of the invention as outlined by the claims. The specifications, figures and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense. The invention is intended to embrace all alternatives, modifications and variations which fall within the spirit and scope of the appended claims. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

[0069] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.