Capacitor with stoichiometrically adjusted dielectric and method of fabricating same

• US 6,566,186 B1
• Filed: 05/17/2000
• Issued: 05/20/2003
• Est. Priority Date: 05/17/2000
• Status: Expired due to Term

• Current Assignee: Bell Semiconductor, LLC (Hilco Inc. (d/b/a Hilco Global))
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Saopraseuth, Ponce, Mansour, Nabil, Allman, Derryl D. J.
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): Thomas, Toniae M.
• Application Number:
  US09/573,137
• Time in Patent Office: 1,098 Days
• Field of Search: 438/240, 438/253, 438/254, 438/255, 438/256, 438/396, 438/397, 438/398, 438/399, 438/786, 438/381, 438/788, 438/792, 438/239
• US Class Current: 438/239
• CPC Class Codes: C23C 16/345 Silicon nitride
• CPC Class Codes: C23C 16/52 Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• CPC Class Codes: H01L 21/0214 the material being a silicon oxynitride, e.g. SiON or SiON:H
• CPC Class Codes: H01L 21/0217 the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz H01L21/02126 and H01L21/0214 take precedence
• CPC Class Codes: H01L 21/02211 the compound being a silane, e.g. disilane, methylsilane or chlorosilane
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/3185 of siliconnitrides
• CPC Class Codes: H01L 28/40 Capacitors

Abstract

A capacitor and a capacitor dielectric material are fabricated by adjusting the amount of an ionic conductive species, such as hydrogen, contained in the capacitor dielectric material to obtain predetermined electrical or functional characteristics. Forming the capacitor dielectric material from silicon, nitrogen and hydrogen allows a stoichiometric ratio control of silicon to nitrogen to limit the amount of hydrogen. Forming the capacitor by dielectric material plasma enhanced chemical vapor deposition (PECVD) allows hydrogen bonds to be broken by ionic bombardment, so that stoichiometric control is achieved by controlling the power of the PECVD. Applying a predetermined number of thermal cycles of temperature elevation and temperature reduction also breaks the hydrogen bonds to control the amount of the hydrogen in the formed capacitor dielectric material.

Claims

1. A method of fabricating a capacitor dielectric material in a capacitor, comprising the steps of:

forming the capacitor dielectric material from substances containing silicon, nitrogen, and hydrogen; and

adjusting a composition of the capacitor dielectric material by controlling a ratio of silicon to nitrogen of the capacitor dielectric material to no more than one in order to adjust an amount of the hydrogen contained in the capacitor dielectric material and to obtain predetermined electrical characteristics of the capacitor, where the predetermined electrical characteristics of the capacitor include at least one of capacitance density, linear response (dC/dV), and leakage current.

3. A method as defined in claim 1 wherein the capacitor dielectric material is substantially silicon oxynitride.

4. A method as defmed in claim 1 further comprising the step of:

controlling the ratio of silicon to nitrogen to achieve a stoichiometric ratio of approximately 0.75 in the capacitor dielectric material.

5. A method as defined in claim 1 further comprising the steps of:

forming the capacitor dielectric material from substances also including oxygen;

controlling the relative proportion of silicon, nitrogen, hydrogen and

oxygen to obtain a stoichiometric ratio of silicon to nitrogen in the formed capacitor dielectric material of approximately 1.0 or less.

6. A method as defined in claim 1 further comprising the steps of:

using silane gas as the substance which includes silicon and hydrogen;

using ammonia gas as the substance which includes nitrogen and hydrogen;

using nitrogen gas as the substance which includes nitrogen;

using oxygen gas as an additional substance which includes oxygen; and

controlling the relative proportions of the silane, ammonia and nitrogen gases when forming the capacitor dielectric material to obtain a stoichiometric ratio of silicon to nitrogen in the formed capacitor dielectric material of approximately 1.0 or less.

7. A method as defined in claim 1 further comprising the steps of:

forming the capacitor dielectric material from substances including silicon, nitrogen and hydrogen;

forming the capacitor dielectric material to include hydrogen bonds therein by depositing the substances by using plasma enhanced chemical vapor deposition;

breaking a predetermined number of the hydrogen bonds to the capacitor dielectric material by ionic bombardment to allow the hydrogen from the broken bonds to escape from the capacitor dielectric material;

controlling the power of the plasma enhanced chemical vapor deposition to establish the extent of the ion bombardment; and

controlling the amount of the hydrogen remaining in the formed capacitor dielectric material by controlling the power of the plasma enhanced chemical vapor deposition.

8. A method as defined in claim 1 further comprising the steps of:

forming the capacitor dielectric material from substances including silicon, nitrogen and hydrogen;

forming the capacitor dielectric material to have hydrogen bonds from the substances;

breaking hydrogen bonds to the capacitor dielectric material by applying at least one thermal cycle of temperature elevation and temperature reduction to the capacitor dielectric material to allow the hydrogen from the broken bonds to escape from the capacitor dielectric material; and

controlling the amount of the hydrogen in the formed capacitor dielectric material by controlling the numbers and extent of thermal cycles applied to the capacitor dielectric material.

2. A method of fabricating a capacitor dielectric material in a capacitor, comprising the steps of:

forming the capacitor dielectric material from substances including silicon, nitrogen and hydrogen; and

controlling a stoichiometric ratio of silicon to nitrogen in the formed capacitor dielectric material to a ratio of approximately 1.0 or less in order to limit an amount of the hydrogen contained in the capacitor dielectric material and to obtain predetermined electrical or functional characteristics of the capacitor;

wherein the capacitor dielectric material is substantially silicon nitride.

9. A method of fabricating a capacitor dielectric material in a capacitor, comprising the steps of:

forming the capacitor dielectric material to contain hydrogen and hydrogen bonds from substances including silicon, nitrogen and hydrogen,

adjusting a composition of the capacitor dielectric material by controlling a stoichiometry of the capacitor dielectric material in order to adjust an amount of the hydrogen contained in the capacitor dielectric material and to obtain predetermined electrical or functional characteristics of the capacitor,

breaking hydrogen bonds to the capacitor dielectric material by applying at least one thermal cycle of temperature elevation and temperature reduction to the capacitor dielectric material to allow the hydrogen from the broken bonds to escape from the capacitor dielectric material, and

controlling the amount of the hydrogen in the formed capacitor dielectric material by controlling the numbers and extent of thermal cycles applied to the capacitor dielectric material,

wherein the capacitor dielectric material is silicon dioxide.

10. A method of controlling ionic conduction in a capacitor dielectric material, comprising the steps of:

forming the capacitor dielectric material from a first substance, a second substance and a third substance, the formed capacitor dielectric material having a characteristic that a stoichiometric ratio of the first and second substances determines the amount of the third substance in the formed capacitor dielectric material, the third substance having the capability to promote ionic conduction in the capacitor dielectric material; and

controlling the stoichiometric ratio of the first and second substances when forming the capacitor dielectric material to control the amount of the third substance in the formed capacitor dielectric material, and thereby control the ionic conduction in the capacitor dielectric material.

11. A method as defined in claim 10 further comprising the step of:

controlling the stoichiometric ratio of the first and second substances to reduce the amount of the third substance in the capacitor dielectric material to approximately its lowest practical amount.

12. A method as defined in claim 10 wherein the first, second and third substances are gases, and said method further comprises the step of:

controlling the relative amounts of gas flow of the first and second substances when forming the capacitor dielectric material to control the amount of the third substance.

13. A method as defined in claim 10 wherein the third substance is hydrogen.

14. A method as defined in claim 13 wherein the capacitor dielectric material is one of silicon nitride or silicon oxynitride.