Method for processing a layer of material while using insitu monitoring and control

• US 5,372,673 A
• Filed: 01/25/1993
• Issued: 12/13/1994
• Est. Priority Date: 01/25/1993
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Turman, Christopher A., Winebarger, Paul M., Ferguson, Gregory S., Stager, Charles W.
• Primary Examiner(s): Breneman, R. Bruce
• Assistant Examiner(s): Fleck, Linda J.
• Application Number:
  US08/008,034
• Time in Patent Office: 687 Days
• Field of Search: 156/626
• US Class Current: 438/8
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step

Abstract

A method for planarizing a layer (18) begins by forming a layer (18) over a wafer having a substrate (12). Layer (18) has a surface topography which is not planar. A layer of material (20) is formed over the layer (18). The layer of material (20) has a surface which is more planar than the surface of layer (18). The surface of material (20) is transferred into the layer (18) by etching the layer (18) and the material (20) at approximately the same etch rate. The same etch rate is achieved by monitoring one of either the surface of the wafer or the etch environment of an etch system chamber. A computer-controlled feedback path alters an etch chemistry or etch environment to maintain the etch rates within an etch rate tolerance which is also referred to as a process window. By monitoring and altering the etch environment and/or the etch chemistry to maintain a process window, an optimal planar surface is achieved for layer (18).

Claims

1. A method for etching a layer of material in a semiconductor etch system, the method comprising the steps of:

exposing the layer of material to an etch environment, the layer of material having a top surface which is a non-planar top surface;

monitoring an etch rate of the layer of material by monitoring an atomic structure which comprises only oxygen in the etch environment; and

altering said etch environment to maintain said etch rate at a selected etch rate which lies within a selected tolerance range in order to planarize the top surface of the layer of material to a surface which is more planar than the non-planar top surface.

2. The method of claim 1 wherein the step of altering said etch environment comprises altering at least one variable within a group consisting of:

semiconductor etch system chamber pressure, semiconductor etch system chamber temperature, semiconductor etch system voltage potential, semiconductor etch system chamber energy, semiconductor etch system chamber dimensions, semiconductor etch system electrode separation, semiconductor etch system gas flow, semiconductor etch system chamber chemistry, and semiconductor etch system ambient gas concentrations.

3. The method of claim 1 wherein the step of altering said etch environment comprises:

altering the concentration of the atomic structure which comprises only oxygen within the semiconductor etch system.

4. The method of claim 1 wherein the step of altering said etch environment comprises:

altering the etch environment in N discrete steps, where N is an integer greater than zero.

5. The method of claim 1 wherein the step of altering said etch environment comprises:

altering the etch environment dynamically, based upon said etch rate.

6. The method of claim 5 wherein the semiconductor etch system has a controller and a chamber, and the step of altering said etch environment dynamically comprises:

alternating said etch environment in an insitu manner via a feedback path which is coupled between the chamber and the controller; and

controlling the feedback path by a computer.

7. The method of claim 1 further comprising:

forming a masking layer comprising photoresist over the layer of material; and

planarizing the layer of material by etching the masking layer and the layer of material at a substantially equal rate.

8. The method of claim 1 wherein the step of monitoring the etch rate comprises:

optically monitoring at least one optical wavelength of the atomic structure which comprises only oxygen in an etch chemistry environment located within the semiconductor etch system.

9. The method of claim 8 wherein the step of optically monitoring comprises:

monitoring a single optical frequency of the atomic structure which comprises only oxygen within a wavelength range of 200 nm to 800 nm.

10. The method of claim 1 wherein the semiconductor etch system etches a semiconductor wafer and the step of monitoring the etch rate comprises:

monitoring a surface of the semiconductor wafer with an energy source to determine the etch rate.

11. The method of claim 10 wherein the step of monitoring the surface of the semiconductor wafer comprises:

using an energy source selected from a group consisting of;

a laser, a collimated light source, and a polarized light source.

12. The method of claim 10 wherein a masking layer is formed overlying the layer of material and the layer of material is formed overlying a semiconductor wafer, the step of monitoring the surface of the semiconductor wafer comprises:

using a first energy source to monitor an etch rate of the layer of material; and

using a second energy source to monitor an etch rate of the masking layer.

13. The method of claim 12 wherein the step of monitoring the surface of the semiconductor wafer comprises:

altering said etch environment to maintain a substantially equal etch rate for both the layer of material and the masking layer.

14. The method of claim 1 wherein the step of monitoring comprises:

monitoring an etch plasma for a change in atomic O concentration.

15. A method for etching a layer of material overlying a semiconductor wafer substrate, the semiconductor wafer substrate being physically supported by a semiconductor equipment system, the method comprising the steps of:

exposing the layer of material to an etch chemistry having a chemical composition which includes an oxygen concentration wherein the oxygen concentration includes atomic structures which contain only oxygen atoms;

monitoring the etch chemistry via an optical detector to determine variations in the chemical composition of the etch chemistry, the variations being detected by monitoring an oxygen emission line corresponding to the atomic structures which contain only oxygen atoms; and

altering the chemical composition of the etch chemistry to maintain the chemical composition within a selected range wherein an etch rate of the layer of material is substantially constant over time.

16. The method of claim 15 wherein the step of altering said chemical composition comprises:

altering the concentration of the atomic structure which contain only oxygen atoms within the semiconductor equipment system.

17. The method of claim 15 wherein the step of altering said chemical composition comprises:

altering the chemical composition by one of either increasing or decreasing a gas flow of a chemical species within the chemical composition in N discrete steps over time, where N is an integer greater than zero.

18. The method of claim 15 wherein the step of altering said chemical composition comprises:

altering the chemical composition dynamically via a computer, the altering being based upon measured deviations in said etch rate.

19. The method of claim 15 wherein the semiconductor etch system has a controller and a chamber, and the step of altering said chemical composition comprises:

alternating said etch environment in an insitu manner via a feedback path which is coupled between the chamber and the controller; and

controlling the feedback path by a computer.

20. The method of claim 15 further comprising:

forming a masking layer over the layer of material; and

planarizing the layer of material by etching the masking layer and the layer of material at a substantially equal rate.

21. The method of claim 15 wherein the step of monitoring the etch chemistry comprises:

optically monitoring at least one optical wavelength of the atomic structures which contain only oxygen atoms within an etch chemistry environment which is located within the semiconductor etch system.

22. The method of claim 15 wherein the step of monitoring the etch chemistry comprises:

monitoring an etch plasma for a change in concentration of the atomic structures which contain only oxygen atoms.

23. A method for etching both a first layer of material overlying a semiconductor wafer substrate and a second layer of material overlying the semiconductor wafer substrate, the first layer of material being different from the second layer of material, the semiconductor wafer being physically supported by a semiconductor equipment system, the method comprising the steps of:

exposing both the first layer of material and the second layer of material to an etch chemistry having a chemical composition, the etch chemistry resulting in a first selected etch rate for the first layer of material and a second selected etch rate for the second layer of material, the first layer of material having an initial non-planar top surface;

monitoring the surface of the first layer of material via a first energy source to determine variations in the first selected etch rate;

monitoring the surface of the second layer of material via a second energy source to determine variations in the second selected etch rate; and

altering the etch chemistry to maintain the chemical composition within a selected range wherein an etch rate of the first layer of material is substantially equal to the etch rate of the second layer of material over a predetermined period of time so that the of material is planarized to have a more planar top surface than the initial non-planar top surface.

24. The method of claim 23 further comprising the steps of:

forming a masking layer of photoresist over the layer of material; and

planarizing the layer of material by etching the masking layer and the layer of material at a substantially equal rate.

25. The method of claim 23 wherein the step of monitoring the layer of material comprises:

using an energy source selected from a group consisting of;

a laser, a collimated light source, and a polarized light source.

26. The method of claim 23 wherein a masking layer is formed overlying the layer of material and the step of monitoring the layer of material comprises:

using a first energy source to monitor an etch rate of the layer of material; and

using a second energy source to monitor an etch rate of the masking layer.

27. The method of claim 26 wherein the step of monitoring the surface of the semiconductor wafer comprises:

altering said etch environment to maintain a substantially equal etch rate for both the layer of material and the masking layer, the altering resulting in a change in atomic O concentration in the etch environment.

28. A method for monitoring a semiconductor etch system environment within a semiconductor etch system, the method comprising the steps of:

placing at least one semiconductor wafer within the semiconductor system, the semiconductor wafer having a layer of material which has a non-planar top surface;

etching the semiconductor wafer in the semiconductor system environment wherein the semiconductor equipment environment contains at least one chemical etch species;

monitoring the semiconductor equipment environment over time with an optical measurement device, the optical measurement device detecting changes in the semiconductor equipment environment over time which affect the processing of the semiconductor wafer by monitoring an emission line which corresponds to an atomic structure containing only oxygen atoms, the atomic structure being present in the semiconductor equipment environment; and

dynamically altering the semiconductor system environment to minimize changes over time which affect the etching of the semiconductor wafer wherein the non-planar top surface is further planarized by the steps of dynamically altering.

29. The method of claim 28 wherein the step of monitoring comprises:

monitoring the semiconductor equipment environment over time with an optical sensor tuned to a frequency substantially equal to 437 nm.

30. A method for etching a layer of material having a nonplanar surface to form a planar surface from the nonplanar surface, the method comprising the steps of:

providing a substrate;

forming the nonplanar layer of material overlying the substrate;

forming a planar layer of material overlying the nonplanar layer of material; and

etching the planar layer of material at a first etch rate and etching the nonplanar layer of material at a second etch rate to form said planar surface on the layer of material, the first etch rate and the second etch rate being kept substantially equal by monitoring the first etch rate and the second etch rate and controlling an etch environment during the step of etching, the monitoring being performed by a method selected from a group consisting of;

(1) monitoring an emission line of an atomic structure containing only oxygen atom(s) in an etch environment and (2) monitoring the surface of the planar layer of material with a first light source, a first beamsplitter, and a first photodetector and monitoring the nonplanar layer of material with a second light source, a second beamsplitter, and a second photodetector.

31. The method of claim 30 wherein the step of etching comprises:

monitoring the semiconductor equipment environment over time with a detection device selected from a group consisting of;

a laser, a collimated light source, a polarized light source, a monochrometer, an interferometer, a mass spectrometer, a spectrum analyzer, and an optical sensor.

32. A method for etching a plurality of wafers, the method comprising the steps of:

placing at least one wafer into a batch semiconductor equipment chamber, the at least one wafer having a non-planar layer made of a first material and a planar layer made of a second material and overlying the non-planar layer, the planar layer being more planar than the non-planar layer, the first material being different from the second material;

placing a monitoring wafer into the batch semiconductor equipment chamber, the monitoring wafer having a first portion which exposes an area of first material and a second portion which exposes an area of second material;

exposing the at least one wafer and the monitoring wafer to an etch environment; and

monitoring the etch rate of the first and second portion of the monitoring wafer to ensure that an etch rate of the first material of the at least one wafer and an etch rate of the second material of the at least one wafer are substantially equal so that the at least one wafer is etched in a manner which increases the planarization of the non-planar layer.