Method for manufacturing a protective layer against hf etching, semiconductor device provided with the protective layer and method for manufacturing the semiconductor device

Patent metadata

Field	Value
Publication number	US-2016130140-A1
Application number	US-201514982380-A
Country	US
Kind code	A1
Filing date	Dec 29, 2015
Priority date	Oct 28, 2011
Publication date	May 12, 2016
Grant date	—

Abstract

A method for manufacturing a protective layer for protecting an intermediate structural layer against etching with hydrofluoric acid, the intermediate structural layer being made of a material that can be etched or damaged by hydrofluoric acid, the method comprising the steps of: forming a first layer of aluminium oxide, by atomic layer deposition, on the intermediate structural layer; performing a thermal crystallization process on the first layer of aluminium oxide, forming a first intermediate protective layer; forming a second layer of aluminium oxide, by atomic layer deposition, above the first intermediate protective layer; and performing a thermal crystallization process on the second layer of aluminium oxide, forming a second intermediate protective layer and thereby completing the formation of the protective layer. The method for forming the protective layer can be used, for example, during the manufacturing steps of an inertial sensor such as a gyroscope or an accelerometer.

First claim

1 . A method comprising:
forming a protective layer configured to protect a structural layer against etching with hydrofluoric acid, wherein the structural layer is made of a material that can be etched or damaged by hydrofluoric acid, the forming including:
forming a first layer of aluminum oxide, by atomic layer deposition, on the structural layer;
forming a first intermediate protective layer by performing a thermal crystallization process on the first layer of aluminum oxide;
forming a second layer of aluminum oxide, by atomic layer deposition, over the first intermediate protective layer; and
forming a second intermediate protective layer by performing a thermal crystallization process on the second layer of aluminum oxide, wherein the first and the second intermediate protective layers form said protective layer.

2 . The method according to claim 1 , wherein said second intermediate protective layer is formed in direct contact with the first intermediate protective layer.

3 . The method according to claim 1 , wherein the steps of forming the first and the second layer of aluminum oxide are carried out in a reaction chamber, each step comprising:
heating the environment inside the reaction chamber to a temperature of between approximately 150° C. and 400° C.; introducing H 2 O vapor into the reaction chamber; introducing trimethylaluminum into the reaction chamber; and repeating introducing H 2 O vapor and trimethylaluminum until a layer with a thickness of between approximately 10 nm and 60 nm is grown.

4 . The method according to claim 3 , further comprising, after introducing the H 2 O vapor and introducing the trimethylaluminum, the method further comprising introducing nitrogen into the reaction chamber.

5 . The method according to claim 1 , wherein each of the steps of performing the thermal crystallization process of the first and second layers of aluminum oxide comprise:
performing a thermal process for a period of between approximately 10 seconds and 2 minutes at a temperature of between approximately 800° and 1100° C.; or heating the first and second layers of aluminum oxide, respectively, in a furnace for a period of between approximately 10 minutes and 90 minutes at a temperature of between approximately 800° and 1100° C.

6 . The method according to claim 1 further comprising:
making a semiconductor device, wherein making the semiconductor device includes:
forming the structural layer of a first material, that can be at least one of etched or damaged by hydrofluoric acid, over a first surface of a substrate;
forming the protective layer over the structural layer;
forming a sacrificial layer of a second material can be etched by hydrofluoric acid, over the protective layer;
forming at least one structural region above and in contact with the sacrificial layer; and
selectively removing the sacrificial layer and rendering the structural region at least partially free-standing above the protective layer by etching the sacrificial layer using hydrofluoric acid or a mixture that includes hydrofluoric acid.

7 . The method according to claim 6 , wherein said first and second materials are chosen from a group comprising at least one of silicon oxide, silicon nitride, oxynitrides and doped oxides.

8 . The method according to claim 6 , further comprising forming an electrical interconnection region at least partially overlapping the protective layer,
and wherein forming the structural region comprises forming the structural region in electrical contact with a surface portion of the electrical interconnection region that is not covered by the protective layer.

9 . The method according to claim 6 , further comprising forming an electrical interconnection region over the first surface of the substrate,
and wherein forming the protective layer comprises forming the protective layer over the electrical interconnection region and covering the electrical interconnection region.

10 . The method according to claim 9 , wherein forming said structural region includes forming a portion of said structural region through the sacrificial layer and the protective layer and in electrical contact with the electrical interconnection region.

11 . The method according to claim 9 , wherein forming the protective layer comprises forming the protective layer over one or more portions of the electrical interconnection region.

12 . The method according to claim 11 , wherein forming said structural region includes forming a portion of said structural region through the sacrificial layer, said structural region being electrically coupled with a surface portion of the electrical interconnection region that is not covered by the protective layer.

13 . The method according to claim 9 , wherein the electrical interconnection region is made of doped polysilicon.

14 . The method according to claim 9 , wherein forming the electrical interconnection region comprises forming the electrical interconnection region over the structural layer, the method further comprising:
forming a support layer, of a third material that can be at least one of etched or damaged by hydrofluoric acid over the structural layer and coplanar with said electrical interconnection region; and forming the protective layer over the support layer.

15 . The method according to claim 6 , wherein said semiconductor device is an inertial MEMS sensor, the structural region being a movable mass of said inertial sensor.

16 . A method comprising:
forming a substrate having a first surface and a second, opposing surface; forming a structural layer of a material that can be at least one of etched and damaged by hydrofluoric acid over the first surface of the substrate; and forming a protective layer over the structural layer, the protective layer including a first intermediate protective layer of crystallized aluminum oxide and a second intermediate protective layer of crystallized aluminum oxide over the first intermediate protective layer.

17 . The method according to claim 16 , further comprising:
making a semiconductor device, wherein making the semiconductor device includes:
forming the structural layer of a first material, that can be at least one of etched or damaged by hydrofluoric acid, over a first surface of a substrate;
forming the protective layer over the structural layer;
forming a sacrificial layer of a second material can be etched by hydrofluoric acid, over the protective layer;
forming at least one structural region above and in contact with the sacrificial layer; and
selectively removing the sacrificial layer and rendering the structural region at least partially free-standing above the protective layer by etching the sacrificial layer using hydrofluoric acid or a mixture that includes hydrofluoric acid

18 . The method according to claim 17 , wherein the steps of forming the first and the second layer of aluminum oxide are carried out in a reaction chamber, each step comprising:
heating the environment inside the reaction chamber to a temperature of between approximately 150° C. and 400° C.; introducing H 2 O vapor into the reaction chamber; introducing trimethylaluminum into the reaction chamber; and repeating introducing H 2 O vapor and trimethylaluminum until a layer with a thickness of between approximately 10 nm and 60 nm is grown.

19 . A method comprising:
by atomic layer deposition, depositing a first layer of aluminum oxide on a structural layer that is made of a material that can be etched or damaged by h

Assignees

• St Microelectronics Srl

Inventors

• Losa Stefano
• Pezzuto Raffaella
• Campedelli Roberto
• Perletti Matteo
• Esposito Luigi
• Urquia Mikel Azpeitia

Classifications

• H10P14/6339

  deposition by cyclic CVD, e.g. ALD, ALE or pulsed CVD · CPC title

• H10P14/69391 Primary

  the material containing aluminium, e.g. Al2O3 · CPC title

• B81C1/00801 Primary

  Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer (B81C1/00595, B81C1/00468 take precedence) · CPC title

• B81C2201/053

  Depositing a protective layers · CPC title

• B81C2201/014

  by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal · CPC title