Multi-step high density plasma (HDP) process to obtain uniformly doped insulating film
View Patent ↗A method of forming an essentially uniform doped insulating layer is disclosed. Variations in a substrate temperature that may result in a dopant gradient within a doped insulating layer can be compensated for by varying a dopant supply rate in a deposition process. One particular embodiment discloses a method of forming a high density plasma phosphosilicate glass having a phosphorous concentration of 8% or greater by weight that varies by no more than about 1% by weight throughout.
1. A method comprising:
varying a dopant supply rate for a doped insulating layer according to a variation in temperature of a substrate on which the doped insulating layer is being formed; and
varying the dopant supply rate includes increasing the dopant supply rate as the substrate temperature increases.
2. The method of claim 1 , wherein:
the doped insulating layer is formed with a high density plasma deposition process.
3. The method of claim 1 , wherein:
the doped insulating layer comprises phosphosilicate glass.
4. The method of claim 1 , wherein:
varying the dopant supply rate includes providing different dopant supply rates for different time periods.
5. The method of claim 1 , further including:
etching a contact hole through the doped insulating layer to the substrate.
6. The method of claim 1 , further including:
varying the dopant supply rate over a first period of time and maintaining a constant dopant supply rate for a second period of time.
7. The method of claim 4 , wherein:
the different time periods include a plurality of time periods of the same length, the dopant supply rate being different during at least two of the time periods.
8. The method of claim 5 , wherein:
the doped insulating layer comprises phosphosilicate glass having a phosphorous dopant concentration of greater than about 6% by weight.
9. The method of claim 6 , wherein:
the first period of time precedes the second period of time.
10. A method, comprising:
compensating for a temperature dependent dopant gradient in a doped insulating film comprising silicon oxide having a phosphorous concentration greater than about 7% by weight, by varying a dopant supply rate as the doped insulating film is formed; wherein
the dopant supply rate is varied for an initial thickness of the doped insulation film to compensate for variations in a substrate temperature.
11. The method of claim 10 , wherein:
the initial thickness is no more than 0.8 microns.
12. The method of claim 10 , wherein:
the initial thickness is no more than 0.4 microns.
13. The method of claim 10 , further including:
varying the dopant supply rate for a first portion of the insulating film and maintaining a constant dopant supply rate for a second portion of the insulating film.
14. The method of claim 10 , further including:
varying the dopant supply rate includes closed loop control of dopant source supply rate with active temperature feedback from a reaction chamber.
15. The method of claim 10 , wherein:
varying the dopant supply rate includes altering a supply rate ratio given by a dopant source supply rate divided by the dopant source supply rate plus a base material source supply rate.
16. The method of claim 15 , wherein:
the dopant source supply rate includes a flow rate for a source of phosphorous, the base material source supply rate includes a flow rate for a source of silicon, and the supply rate ratio varies from about 30% to 45%.