Method and device for controlling the thickness of a layer of an integrated circuit in real time

• US 6,746,881 B1
• Filed: 11/17/2000
• Issued: 06/08/2004
• Est. Priority Date: 11/23/1999
• Status: Expired due to Term

• Current Assignee: Atmel Switzerland SARL (Microchip Technology Incorporated)
• Original Assignee: Atmel Nantes SA (Microchip Technology Incorporated)
• Inventors: Charpentier, Alain, Bocquene, Dominique
• Primary Examiner(s): Coleman, W. David
• Assistant Examiner(s): Kebede, Brook
• Application Number:
  US09/714,524
• Time in Patent Office: 1,299 Days
• Field of Search: 438/14, 438/16, 438/18, 438/257, 438/FOR.101, 438/FOR.142, 356/357, 356/369, 356/381, 356/382, 257/E21.521
• US Class Current: 438/14
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

A method and a device for measuring in real time the thickness of an integrated circuit layer with the layer to be measured being deposited on an underlying layer. During an engraving operation, the advance of the engraving front generated during the engraving operation is monitored by plotting the optical emission spectrum of the product of the engraving reaction in real time on a spectral component of the underlying layer. A time distribution of the optical emission amplitude of the engraving reaction product is established and the transition of the optical emission amplitude on the distribution as the engraving front passes from the layer to be measured to the underlying layer as established. The thickness of the layer to be measured is thus computed on the basis of the distribution and the transition by a correlation with the transition on the distribution.

Claims

1. A method for measuring a thickness of a first layer,

said first layer to be measured being deposited on a second layer which is underneath said first layer,

said first and second layers being part of an integrated circuit,

said method being carried out, in real time, during an engraving reaction wherein an engraving front progresses from said first layer to said second, underneath layer,

said engraving front progressing at a predetermined speed, and

said engraving reaction, when applied to said second, underneath layer, generating a light emission having at least one spectral component,

said method comprising the steps of:

a) measuring an amplitude of light emitted during the engraving reaction, in a selected spectral range comprising said at least one spectral component;

b) establishing a distribution of said amplitude as a function of time;

c) determining, from said distribution, a moment of occurrence of an increase in said measured amplitude, said moment corresponding to a point in time at which the engraving front reaches the second, underneath layer;

d) and computing the thickness of said first layer to be measured, on the basis of said moment and said predetermined speed of the engraving front.

2. The method of claim 1, wherein said spectral component of said underneath layer is a perceptible emission wavelength characteristic of said underneath layer.

3. The method of claim 1, wherein said first layer to be measured comprises a layer of silicon oxide and the second, underneath layer comprises a barrier layer of silicon nitride, and wherein said at least one spectral component of said light emission generated when said engraving reaction is applied to said second, underneath layer is a spectral line SiN at 405 nm.

4. The method of claim 1, wherein:

distribution starts from a beginning time of the engraving reaction at which said amplitude constitutes a reference amplitude, and

a further time, corresponding to said moment, when said amplitude reaches 150% of the reference amplitude.

5. The method of claim 1, wherein the step comprising measuring the amplitude of said light emitted is performed by means of a monochromator.

6. A device for measuring a thickness of a first layer,

said first layer to be measured being deposited on a second layer which is underneath said first layer,

said first and second layers being part of an integrated circuit;

the measuring of the thickness of said first layer, in real time, during an engraving reaction wherein an engraving front progresses from said first layer to said second, underneath layer,

said engraving front progressing at a predetermined speed, and

said engraving reaction, when applied to said second, underneath layer, generating a light emission having at least one spectral component,

said device comprising;

first means for measuring an amplitude of light emitted during the engraving reaction, in a selected spectral range comprising said at least one spectral component;

and second means for;

establishing a distribution of said amplitude as a function of time;

determining, from said distribution, a moment of occurrence of an increase of said measure amplitude, said moment corresponding to a point in time at which the engraving front reaches the second underneath layer; and

computing the thickness of said first layer to be measured, on the basis of said moment and said predetermined speed of the engraving front.

7. The device of claim 6, further comprising:

a reactor for engraving said integrated circuit, said reactor being fitted with an optical window enabling the engraving reaction to be optically observed;

a monochromator, the wavelength of which is centered on a characteristic value of said second, underneath layer, for enabling amplitude values of the emitted light to be measured; and

means for determining a time period taken by the engraving front produced within said reactor to reach the second, underneath layer and for computing an effective thickness of said first layer to be measured by a linear combination linking said effective thickness to the time taken by said engraving front to reach said second, underneath layer.